HecRas 6.3.1 2D flow modeling for beginners

hello everyone my name is behnam today I want to explain a little about how to modeling of fellow in a class 2D the last version of 6.3.1 I record this video for the ntnu hydraulic modeling course and I will explain a little about how to model A River Ridge and how to inject the results and improve the results for example improve the mesh that we have how to improve the other parameters that we have so for the start we should go as you are now familiar with the class software you know that we should first make a project so I recommend to uh first check the previous check the previous video that I upload for the 1D so this is the so I name it like for example lardol be careful to not use the special letters in other language like Norwegian or German so for starting we should go to the last mapper after also checking the unit as we discussed about it the unit should be s i so here for 2D modeling we should introduce a terrain and first as you see we have a message to add the projection file here we can have the projection file or you can go to the just projects set projections this is the projection that we have and you can see the zone is 32n as I mentioned before you can also find any uh projection file if you have any problem with your projection file or if you want to search for your projection file which I can just go to this website special reference.org and then search your name for example or if you have this number you can search it or if you have the UTM for example this one you can search it and you can find the new 10 gold you can find a new rejection file then go to the train create a new rest train to introduce your Thief file here you should go to the plus and come here you have a t file if you have more diff file you should add all of them and then click the merge input to single single raster then create it it takes a little time then after that you can go to the map layer and you can add the Google image or Google satellite and also add other points that you have or other layer that you need and as I explained before in the geometries you can see the geometries input and your mesh and in the result after you run the model you can see the results so now it's finished and you can see the river that we have so then I'm going to the for example add reference if you want to add the same train as the terrain that you have you can add a layer here or if you want the image you can go to the Google satellite for example and then add you can see it in the options you you have some options like capacity you can change the capacity you can see the overlay of the images and then save and exit then for introducing the 2D flow mesh we should go to the geometry here or edit geometry now we should introduce a 2d fellow area so we click here and introduce the area that we want to model the area that we think it's affect from our flood or from our maximum flow that we have so for example I like to model from here so I try to make a Zoom like this and then as I want to be a short one then I just make like this it depends on you for example I make it a big one now to be sure and also fast but you can use the real all right and accurate data so now it's a geometry for example I just wrote the geometry or I can write it like lardol and then okay if you are coming here to the rasmapper you can go to the plot Contours and make it as something like this now you can see the area that you have I think we should increase it a little yes now you can choose the center line of the river if you want or the banks easily by this but as we don't need it then I turn it off but when you want to draw a bank or any line I recommend to turn the control lines on okay and then we left click and go to the edit pillow area here you can see the morning and value we should calibrate this value or we should measured or compute the best value of morning roughness that we have we can use the money and value as you can see 0.06 or 0.04 it depends on the case that you have and for your mesh we should here introduce the mesh I just use it 10 by 10. again it depends to your accuracy and your model you can increase it or decrease it but as I want to be fast and almost good result so I keep it as 10 then generate points in 2D fellow and then the important things Force mesh computation here you can see the information about the mesh and then okay so now you can see the mesh here so then we should introduce the boundary condition lines you can see BC lines here for the boundary condition lines you can get these area for example as we know the river are here just look at how I introduce it so it's the upper stream boundary condition and we need another one it's a downstream if you think you have water also here then you can also introduce the other Downstream that area we have uh here's more important options like 2D area break lines I will talk about it at the end of the video and also the 2D mining regions if you want to if you have a mining layer for example you measured morning roughness along the river in various locations that you can see then you have a morning layer and you can introduce the morning layer to the model and it's really increased the accuracy of your lizard results then I save the geometric data you can name it like geometry and then okay then close it now we should introduce the honestly below data so we are here and we can see we have upstream and downstream data for the upper stream I it depends on your project but we can introduce a fellow hydrograph as we have a discharge I trigger off foreign so here we can start from 65 65 so we run it for the discharge of 920 and then here we need to introduce the slope so we assume the slope is 0.01 or you should compute it from the rasmaper and then okay if you want to see the slope you can come here so this is your River just go to the ruler and then this is an easy way to show that but you should be careful it's not you can see the slope is point zero zero three but it's not accurate because I just draw it without any details if you want to dero it you should and also you should take along the rivers to see the a slope that you have so but one easy way is this okay here then then for the downstream you can have a normal depth if you choose the normal diff here you should introduce the a slope that you have or you can introduce a stage hydrograph so here we have a message that you introduce normally do you want to change it yes we want to change it to the depth and then for the depth we want to have it as a 1.24 so 1.24 I just copy paste it for some values you can assume that your water level is constant or you should introduce a normal the usually I recommend to use the normal debt if you don't have a specific data because according to the changing of the discharge the water level Downstream should be changed it depends to the case that we have if we have a Backwater for example Downstream we have a sea or ocean it's maybe we have a Backwater so we should be careful about these data because after running the model then we should calibrate the model and calibration we should have some major data from the field uh I don't use any major data from the field in this example but you should find the measured data and calibrate your model by matching or having a good agreement between the measured data and your model data so I write it as a queue of 920 and then okay so if you have an initial condition you can add the initial conditions here but we don't need it now and we I I will also also explain for you how to make a hydraulic warm-up which is so important and uh it's a when especially when you don't have initial condition then it is really helpful unnecessary and really really necessary when you have a sediment in your mother then we can go to the honest study file save as we have the previous one so it's 900 20 so Q and then okay for the plan we can name it 0 1 or 0 1 9 uh CMS if especially if you have more plans and more run it's really important to choose a good name and then as we don't have a sediment we just tick these things and it is really important to match the data or the date that you have here with the geometry with the unesthetic data that you have so I choose it today time is zero and then again today time is six you can go and check here on a study fellow data I took it off we have like the time of five five a.m so just look what's happened I can also change these things one second five minutes so this is the computational interval delta T this is the mapping output interval five minutes and its uh effect on the time because it's overwrite or write the result so if you make it less or make it higher its affect the time of your modeling and hydrocraft output interval we can use as the input one that we introduced to the model as one hour but we just keep it like that and the computational interval which is so important for the stability of our model we can keep it as one second and then we push the compute so now you can see we got the error as I told you because the time of the simulation here is not match with the input data so we should change it to five and then if we run it it's run but I would like to explain you about some important options that we have in flow modeling if you click here or if you are coming here computational computation options in options you can see this is for 1D understudy this is for 1D 2D understudy you can see the gravity and other parameters we also have them here I explain them here which are more important these are some values which we don't work with them usually but you can go to the I really recommend you to go to the Acres a manual or request reference and read about the parameters but some of them which are important I explained to you for example you have values equation diffusion wave which generally gives you more accurate results but it is not recommended if you have a sediment modeling you should use most probably as w e uh Elm it's also faster but it depends to your case and you should calibrate your model and see the data but I keep it as diffusion the maximum iteration is 20 it's the maximum number of iteration that you can have if you decrease it you may have maybe faster modeling but instead you'd also increase the instability and also some other variables that you have here so if you want the turbulence model you can use the conservative or non-conservative in the reference you have some recommendation for example if you use the s w e e l m equation it is recommended to use the conservative form and there is for example a table in a request manual that explains these things very well to you an initial condition an initial condition ramp up fraction I explained to you later for example you can put this one as 20 and this one has a two just keep this as a 10 and this one is 0.1 it can be till uh point five I explain any what is the definition of these and then okay and then compute so we have a error here and usual error you can read it always errors give you some information that helps you for example was not created successfully it's a normal error if you can close it and then go to the geometric data and then right click on the edit fellow area and then Force mesh recompassion recomputation again this is happens uh sometimes and you have to recompute the mesh for running the Acres I would like to also here told you if you right click on your mesh you can go to the view options here you can see values option for example if you want to fill it you can feel it or other options that you have to change the view of the geometric data then I like to save it exit and here run and compute it now I explain you what is the hydraulic warm up which is very very important in sediment modeling and also here and I show you by a and I show you by a graph here you can see the models information and the runs and the warm up that we had here it's I if you remember I add 10 now from minus 10 till 0 we have a hydraulic warm-up that you can see here so let's go to the data we have honestly fellow data and below hydrograph you can plot the data and here you can see the data I like to draw these so we just use a assumption for the an STD hydrograph that we have so in the real scenario you use a real hydrograph but again in the hydrogara for example I just try to show you the hydrograph that we have the hydrograph that we use it's like this here it's 65 and here it's 900 20. so the 10 values that we used is a hydraulic warm up and it's so usually from if we want to avoid the shock to our model so we it is better not to start modeling from this high value of discharge so it is better to start from like discharge of zero and gradually we increase it till 6 65 discharge so some researchers or some modelers use a synthetic hydraulic discharge at some values before that but I really recommend to use this interesting option of hackers especially for the sediment modeling it's really important to use it so the first value that we use 10 it's just to increase 10 10 hours of modeling which I add a lot because our modeling is just five hours and I add a lot and what is the ramp the ramp is the one point uh point one is the slope of T still discharge of zero the maximum of ramp value is the 0.5 which is like 45 degree the angle of this I think it's it will be 45 and it's the maximum one if you want to have a like mild slope or high slope so I really recommend to use this so this is discharge and this is time so this is the value that I told you I change it to 0 because we I want to be so fast and we keep it this one as a point one and if you have so many uh runs with so many cores you can also decrease these chords because for a class it is really important to have a course with high speed instead of having so many cores like 60 cores with loud speed then the other important things here you can change the time step instead of fixed time step you can change it to the adjust time step delta T in the headrest is a model parameters so you can change it but it's not necessary to have it like 1 or 12 like 1.2 it converts the results to a stable stable results so you can use like one here but you can also use two and then the minimum Quran should be more than half of the two and then you have a number of steps below minimum for example you can change it to four and maximum number of doubling you can change it to four I also use this one to four here you can see the maximum number of uh time step that hecaris or your model will use is 16 seconds and then the minimum is 0.06 so if your results are not stable then the the model decrease the delta T to this value and if it is stable so for having a a faster result it may choose the bigger one the 16 or between these values I think 2 is a good value but you can also use one it depends on your modeling or result but both of them should be good according to my experience then you can have a result here you can see the results that you have here you see the number of your plan and some information here so we don't have any error here but if you run it you can see the number of iteration here it's 2 3 or it's reached 20 and if it reached 20 then you have the sales number of the errors that you have here and you can find the sales number so as I change the delta T here I just run it to show you it is correct you can see here we receive the error the advanced time is the control requires that the minimum current is less than half of the maximum so I I change it to this value and then you can see it's run but I stop it because with the previous one it's done okay now we are going to the last mapper to see the results you can go to the result and for example show the depth if you play the depth you can see it's changed so if you want to change it for example go to double click on the color button then here change it to two you can here have a different colored but the depth is this or you can also increase the classes then create map value and then okay now you can see the results again or if you want to see the vectors you can use this one or if you want to see the animated vectors you can add this one this is also some options that you have for the vectors over here you have some other parameters this one is uh useful for example you said okay our accuracy is not like one millimeters I want to increase it to one centimeter then you delete this one and okay and you delete the water depth below that that value like one centimeters another important thing that you should learn how to work with this what is these options for example palette if you tick this one you can see the flow connectivity of them so we want to evaluate these the follow and the vectors you can see them everything is seems correct till here so we have a wall here but the water goes to the other size exactly at this time so what's happened as the over mesh is large then we have some cells like this one half of them is in the water and half of them is in the on the wall then the water from these cells coming here and what's happened to the connectivity cells that I show you it shows the connection of the cells you can see the water one comes here the water comes from here this cells and here you have also other parameters 2D gravitation it's we have values vectors here which vectors show different options the blue Vector is a normal fellow the green one here is a intermediate fellow depth the yellow one is the shallow fellow depth here for example to pick the pink one is the critical depth and the gray one is a back water it's like the hydraulic connectivity shows you the errors which cells the water goes from which cells and coming from which cells but I really like this one especially for the not so professional modeling and also you have others for example display arrival time or other parameters that you can use here and they are useful then you have zoom to layer you can Zoom to layer like this and also see the results if you click on right click on this manage the results here you can add each results that you want for different geometry or here create new results so you have hydraulics or two dehydrolics in Hydraulics for example you can use the shear stress we should wait till this finish or other parameters that you have and you can also choose a specific time or you if you want to save it as a train file and of anything the arcgis I recommend to use these options here this one so here for example we can see the results so here it's a shear stress for a specific time you can see it's 50 round 50. so if we want to change this so like from 0 to 60 you can see the results of Shear still isn't if you play it it's increase or you you can see the results of fruit or if I right click on it then go to the create new results and to the additional 2D variable if you want to check your results here you have a cumulative iteration if you click on this especially for the when you have a sediment this option it's useful cumulative iteration or maximum water surface error so here we don't have any uh accumulated spatial accumulative iteration and actually it's not reading but then on the cells you can see for example maybe here we have some values or you know where is the problem with the mesh and in the geometric you can show your mesh here you can see the mesh and if you have like a cumulative errors cumulative iteration here you know that you have a lot of iteration here so there is a problem most probably with the mesh or with the slope that you have here and you should fix the problem I explained a little about how to fix the problem for the mesh and then maximum water surface error you can see the points that we have for example here we have a huge maximum iteration it's it's a maximum point so we can go and fix it so one reason is that this cell is half of on the river region of of them on the wall let me if I can so we don't have this result now okay then I think we are finished here so I close it so then if you need to have another run for another discharge again go to the honestly fellow data and change the parameters here and then save as as another uh fellow data like uh q60020 CMS foreign second so now I would like to show you the 3D results so let's see the depth here it's great then go to the 3D results and okay yes so here in the 3D View we should Zoom a little and then by right click you can turn it and I play it and you can see the here you see that we have a water comings from these cells but we have a wall so data wall is more than the water elevation so we shouldn't have any water here so what should we do we should go to the geometry data and then we have two options first to use break lines to modify the mesh and then we should we can use the refined version for the to define or refine a mesh so I am going to that and show you how to work first with brake lines so what should we do for fixing this problem we should have a break line and I recommend to make this at the starting point of your defining the mesh I just do it now because I want first you learn what is the difference and what is your options so we are going to the 2D brake lines and then I just make it so fast here but you should have a details on that and put time to have a good defining so I make it as a left brake line and then okay then I should also introduce another one at the right so right correct line it is very very important especially when you have a it depends when you have another format of the river you should Define direct line at the bottom of the your bank and at the top of your bank or flat billing and one at the middle of the River or the center line of the river and how to choose the center line I explain it in a previous video for the 1D modeling you should choose the you should go to the rasmaper and then choose the contour lines for example here you should go to the double click and you can use the contour line and then you can see the convalues Contours and you can easily find the bottom of the river but now we just use these two and then after drawing the two break lines they are coming here to the GIS tools and then brake lines cell spacing you can see the various product lines that we have here minimum value of the distance from the background or the maximum for example we can make it here as a 5 and here as a 5 for both and then okay and then I just right click on that and enforce correctly they are also enforce recline you can see the meshes start from these lines and you can also increase these values or decrease these values in that option that you have but we have a problem here it defines one important things for the haircuts mesh it is really important that you don't have a very a small edges like this one it is better your mesh is between like four and six uh like rectangular but you know these a small Edge it's not good for haircuts and you have error for that but if you want to add or remove any points you can go to the edit add points or remove points for example this one I just remove it then you can see we have a new Miss so I just check if we have any other error so we have another arrow here so we can remove it or we can add another point or right click so as you see it seems the mesh is good without error so we save it or it is better to save as it another one and then go to the Run on a steady flow I changed safe plan as this one with break line okay and this one bit correct line and then compute it so here in this case as we change the time instead we make a dynamic time step you can see the model use values time as time steps or delta T like 8 2 4 so it's really useful for uh optimize the time consuming of your model so I close it and then let's go to see the results on Rust mapper foreign so I changed the Contour to maximum of 2 then create and ok and then close it I hope we can fix it so as you see it is really let's see if it is improved so we have it on 2 and 15 the previous one here we have it as almost 1 hour and 30. minutes 35 minutes but as we improve the results we improve the mesh now we have it on almost two hour and 20 minutes so if you do it in a really accurate way just zoom it and make the brake lines very well and use the brake lines at the middle of the river at the bottom of the bank and the top of the bank you can have a really good results very well the next options for defined mesh it's instead of using brake line it's using the refine version I just go to these break lines and delete the brake lines here click delete the break lines and then go to the edit flow and just make it as before then okay then Force to compute and you can see we have a previous mesh and then save it so then after we delete the break lines now we have a refine we have a normal mesh so I save it and then exit so for the defining the refine zone or Define mesh you should go to the rasmapper and then geometry to the fellow area and then you can see break lines or refined mesh I click here and right click edit geometry or you have it here so we are going to the ETI geometry now we can draw a refine mesh so for this purpose I told you that it is good to have a contour line then I click ok now you can see we have a controller and I can also turn off this so it is better to have a like so now you can see the refine mesh and also in the geometry you can see the points or the area that we have so for the defining the refine region we can go like this and we Define area with water I just defined this area to make everything faster and then double click then you have a it's so region I just call it as region one and then okay so now you have you can go to the edit Define region parallel 30s you can see the cell size we can add it like five in eggs and five in y you can have a power spacing nearest spacing nothing we can have it as 10 as 10 to be fast and then you can go to the enforce our regions and then have a this area let me just turn off the layer so we have this layer so you can see the mesh start from this area and then it's again the same so it is it is I really recommend to continue it because then you don't have problem it's continued it's it's sometimes good for like a berated River if you have that you are very respirated with a loud with the course mesh or find mesh so I think I just want to show you how to work so we just keep it simple as this but you please remind that it is really recommend to continue it till here and if I want to model this with the refinement regime I will continue it to the end of the reach so then stop yes save it and then you can see it's saved and then save the total and then exit now here we can make a save plan as so wheat refine region I just name it as RR and here with refined region then okay and compute it we can now see the effect of the reform region if we have any errors or problem or if we can fix the that area that we had problem because of the cell size foreign is finished you can see the time is step and if you have error you don't have error here but if you model the sediment then you have arrows and you have more challenges then go to the rasmapper to see the results very well so here so I try to turn off the geometry turn off this layer and then go to our train so it is better to turn off the Contours and now it's with refine region then we have depth and then make it as two create ramp so let's see if again we have this problem or not but anyway if we have it or if we don't have it it's a way of calibration and the first step is you have to make a really good mesh according to your geometry and your train so let's start okay now we have again this problem but as you can see the it's again occurred in the previous time but here we have it at 2 hours and 20. so you can see the differences of these uh methods and the accuracy of them so first according to your River Reach I recommend to see what is the length of your River Ridge for example you can use the ruler and come here and see okay what is it you can see the length is 50 meters almost 50 meters so a mesh like 5 meters or even 10 meters maybe it's a good as a course mesh of course and then try to refine the center line of your River then the bottom of the banks and then the top of the banks and then introduce the accurate flow data and run your model and enjoy your modeling so now I would like to show you how can we modify the train so you can right click on the train and use the calendar and it's like a virtual copy of your train and you can change and modify it without make any change on your real train so if you right click on this and go to the add new notification layers you have various shapes lines polylines to modify your trend for example if you have a whole or a problem in your on your train then you can use autofill Note data regions then you click on it okay so we don't have any problem on this train but I would like to show you for example imagine that you don't have data here then you just make a modification and it use the elevation of the neighbors and interpolate the trend so you can choose a name and you can also choose the notification method use the replace terrain values higher values add constant values or here you can use the constant value but please just keep the default values and you can also always check if I press F1 what is these parameters so now I would like to run the model with the make a channel so I just go to train then right click add new modification layers go to lines and channels so by a line we would like to make a channel so I would like to make it as here so you can see the name and everything for example I like to change the bit as 15 and make this as 3 3 or this one as just keep it as 100 and you can see the stations and the elevations so I like to change this to 2.3 or this one is two just two then you can see the values and then okay so we make the channels so then I like to save it and then exit save and run the model so you should go to the save calendar then make a new plan so I made it before and then compute it here you can stop your simulation and you can pause your simulation and if you want to check the results which I always recommend to check your results before finishing the results so then you can make a snapshot and come here to check your results so here you can see the results or the velocity just need the modification of results I believe 2D modeling of hello it's easy then in the next videos I will explain how to model the sediment then in that videos I will explain a step by step the flow first so you have that modeling from beginning till to the end without any tests here I try to explain and show you some tests without Define after mesh or redefine the mesh but in the sediment modeling the next video I just will show you how to model follow very fast so you also have another video for learning how to model the flow and then with the more focus on sediment

Channel: Behnam Balouchi

Views: 30,833

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Id: gtfRvM4h0SY

Length: 60min 17sec (3617 seconds)

Published: Tue Feb 07 2023