Excellent video, thanks for the explanation. If the suboff has a vertical part which is above the water how will the bounday definition change? How will vof model change? As the part above the water is mainly under aerodynamic force rather than hydrodynamics.
Dorood Mr. Amiri, This was a great tutorial. I was wondering though about a simple confusion of mine that CFL is measured based on velocity, temporal discritization and spatail discetrization, and usually 0.25 is selected for it. WHY did you select 95?
Dear Shayan, thank you very much for your comment. Note that the condition of having a CFL less than 0.25 is generally more important, when the problem is transient in nature and we are interested in time-varying variables.
Great video! Helps a lot! So if I want to simulate a ship in shallow water waves, are the equations estimating wave length, wave period, and damping constants still applicable?
Plus, I have been searching for the 2016 paper, but it is so difficult to acquire it without a name. Is it possible that you post a link or simply the name of that paper? Really appreciate it.
Dear Ian Zhang, Thank you for writing! In case where you seek to simulate a ship in shallow water waves, you need to use the dispersion relation for shallow waters. Hope this helps. Respectfully, Mojtaba Maali.
Mr. Amiri, Thank you very much for this great tutorial. I want to make similar analysis with different body forms. I have a few questions. @03:58 can't we use ITTC guidelines to define dimensions of computational domain? @08:39 is f2=0 for all applications? @13:00 would it effect meshing process if we multi-choose towing tank and main body and apply "create mesh operation -> boolean -> subtract -> target part:towing tank" @25:30 if we are analysing a ship, how can we decide minimum cell size? @26:10 how can we calculate wave height to devide it10 or 30 if we don't have any experimental data? @28:10 you set minimum face quality 0.2 , can't it be as its default value? @29:19 why did you set "layer reduction percentage" as 0.01? @29:45 you set "target surface size" and "minimum surface size"'s "percentage of base" values as 0.675, it made the absolute size as 0.0067, is that value about wavelength? why 0.675? @30:47 why did you set "max cell size"s "percentage of base" as 100? @33:24 why did you set "surface control2 -> percentage of base -> 86.4"? why not 100? @36:26 why did you set height of "freesurfacecoarse" block as 1m? @40:21 you created a block to make another volumetric control around DARPA, how did you decide the dimensions of that block? and why its trimmer is isotropic? and why its percentage of base is 2.7? Again thank you very much for this amazing detailed tutorial. Yours sincerely.
Dear Mesut, thank you for your comment! I have briefly answered you questions, however, most of them can be deduced by watching the present our other videos in my channel. here goes the answers: @03:58 can't we use ITTC guidelines to define dimensions of computational domain? Sure you can @08:39 is f2=0 for all applications? No, it is not. It is recommended for cases where you are calculating a steady state solution. @13:00 would it effect meshing process if we multi-choose towing tank and main body and apply "create mesh operation -> boolean -> subtract -> target part:towing tank" I dont think so. @25:30 if we are analysing a ship, how can we decide minimum cell size? You can consider the ship hull under water as a half-submarine body. @26:10 how can we calculate wave height to devide it10 or 30 if we don't have any experimental data? Well, for these cases, the best way is just try and error. Or you can use the Adaptive Mesh Refinement technique. @28:10 you set minimum face quality 0.2 , can't it be as its default value? The better the mesh quality, the better will be the results. @29:19 why did you set "layer reduction percentage" as 0.01? To avoid the boundary layer reduction as we approach a sharp variation in geometry. @29:45 you set "target surface size" and "minimum surface size"'s "percentage of base" values as 0.675, it made the absolute size as 0.0067, is that value about wavelength? why 0.675? I have explained my choices in the video, please have a look at the video. @30:47 why did you set "max cell size"s "percentage of base" as 100? This is the maximum cell size within the domain, which will be 1 meter. This is an acceptable value for the maximum cell size within a computational domain. @33:24 why did you set "surface control2 -> percentage of base -> 86.4"? why not 100? Please have a look at this video: ruclips.net/video/6qRPOqXgjNc/видео.html @36:26 why did you set height of "freesurfacecoarse" block as 1m? To cover the whole submarine body and at the same time to ensure a smooth mesh transition. @40:21 you created a block to make another volumetric control around DARPA, how did you decide the dimensions of that block? and why its trimmer is isotropic? and why its percentage of base is 2.7? I have explained this in the video.
Thank you for this impressive tutorial, very interesting, but in 24.19 minutes, I made some calculations based on the equation given, i got m = 31.06 not 23? correct me if I'm wrong? Tq
Great tutorial! It was very helpful! I have one question: How do you determine the angle theta? (The angle between SUBOFF's travel direction and the crest of the waves )
Thank you for this comment. In order to find this angle, you need to first identify the position of the wave crests (at least two), then you can interpolate a line through thee crests, which consequently can be utilized to compute the angle between the SUBOFF and the propagating waves.
@@MohammedKhantheacademicianyou can export the solution data into a spreadsheet and then find the position of the wave crests using another code, such as MATLAB.
@@CFD_Mojtaba to get a solution, I must perform a simulation, to perform a simulation I must enter also specify wave length damping factor, to specify damping factor need to know the theta. I don't know where I am missing something.
thank you very much and great explanation and really appreciated, could you share to me the simulation file and CAD for DARPA, and do you have the appendage DARPA CAD?, i would love to try to do it for my practice purposes and study. thank you.
Sir, actually i model the background like you model it for buoy motion tutorials and for air-supported it is a box structure open at bottom but in starm ccm, I was unable to model the opening at the bottom, so I thought of assigning some boundary conditions to the bottom and sir i have a question how can i model air inside the box and tell me how i should model so that backgorund water should go inside it to compress air.what boudary condition i should assign for open part initially it is wall.@@CFD_Mojtaba
so good！！！！ I want to know how to calculate resistance without additional devices， can you give me some advice or show me the paper address thanks so much！
Thank you for this great tutorial, very helpful how you explain the reasoning behind your approach.
Excellent video, thanks for the explanation. If the suboff has a vertical part which is above the water how will the bounday definition change? How will vof model change? As the part above the water is mainly under aerodynamic force rather than hydrodynamics.
Thanks you! Very interesting and informative tutorial
Great Tutorial ! Please simulate a soccer ball drag force with Star-ccm+ .Thanks .
Dorood Mr. Amiri, This was a great tutorial. I was wondering though about a simple confusion of mine that CFL is measured based on velocity, temporal discritization and spatail discetrization, and usually 0.25 is selected for it. WHY did you select 95?
Dear Shayan, thank you very much for your comment. Note that the condition of having a CFL less than 0.25 is generally more important, when the problem is transient in nature and we are interested in time-varying variables.
my star ccm have missing node under tools>update event how can i fix it?
Hi!Thank you for this great tutorial~ Do you know how to get the RAO number of a ship? I can't find the relevant settings in starccm+
Dear zyh,
The RAO of a ship is obtained through the simulation of the vessel at various wavelengths.
Att,
Mojtaba Amiri.
Can you make a video on ship hull on the mean surface.
Thank you for this interesting tutorial. Can you give me how calculate the wetted length and wetted area.
Very well-done!!
Great video! Helps a lot! So if I want to simulate a ship in shallow water waves, are the equations estimating wave length, wave period, and damping constants still applicable?
Plus, I have been searching for the 2016 paper, but it is so difficult to acquire it without a name. Is it possible that you post a link or simply the name of that paper? Really appreciate it.
Dear Ian Zhang,
Thank you for writing!
In case where you seek to simulate a ship in shallow water waves, you need to use the dispersion relation for shallow waters.
Hope this helps.
Respectfully,
Mojtaba Maali.
Dear Ian,
You can access the article here:doi.org/10.1080/09377255.2015.1119921
Respectfully,
Mojtaba Maali.
@@CFD_Mojtaba Many thanks!!!
Mr. Amiri,
Thank you very much for this great tutorial.
I want to make similar analysis with different body forms. I have a few questions.
@03:58 can't we use ITTC guidelines to define dimensions of computational domain?
@08:39 is f2=0 for all applications?
@13:00 would it effect meshing process if we multi-choose towing tank and main body and apply "create mesh operation -> boolean -> subtract -> target part:towing tank"
@25:30 if we are analysing a ship, how can we decide minimum cell size?
@26:10 how can we calculate wave height to devide it10 or 30 if we don't have any experimental data?
@28:10 you set minimum face quality 0.2 , can't it be as its default value?
@29:19 why did you set "layer reduction percentage" as 0.01?
@29:45 you set "target surface size" and "minimum surface size"'s "percentage of base" values as 0.675, it made the absolute size as 0.0067, is that value about wavelength? why 0.675?
@30:47 why did you set "max cell size"s "percentage of base" as 100?
@33:24 why did you set "surface control2 -> percentage of base -> 86.4"? why not 100?
@36:26 why did you set height of "freesurfacecoarse" block as 1m?
@40:21 you created a block to make another volumetric control around DARPA, how did you decide the dimensions of that block? and why its trimmer is isotropic? and why its percentage of base is 2.7?
Again thank you very much for this amazing detailed tutorial.
Yours sincerely.
Dear Mesut, thank you for your comment!
I have briefly answered you questions, however, most of them can be deduced by watching the present our other videos in my channel.
here goes the answers:
@03:58 can't we use ITTC guidelines to define dimensions of computational domain?
Sure you can
@08:39 is f2=0 for all applications?
No, it is not. It is recommended for cases where you are calculating a steady state solution.
@13:00 would it effect meshing process if we multi-choose towing tank and main body and apply "create mesh operation -> boolean -> subtract -> target part:towing tank"
I dont think so.
@25:30 if we are analysing a ship, how can we decide minimum cell size?
You can consider the ship hull under water as a half-submarine body.
@26:10 how can we calculate wave height to devide it10 or 30 if we don't have any experimental data?
Well, for these cases, the best way is just try and error. Or you can use the Adaptive Mesh Refinement technique.
@28:10 you set minimum face quality 0.2 , can't it be as its default value?
The better the mesh quality, the better will be the results.
@29:19 why did you set "layer reduction percentage" as 0.01?
To avoid the boundary layer reduction as we approach a sharp variation in geometry.
@29:45 you set "target surface size" and "minimum surface size"'s "percentage of base" values as 0.675, it made the absolute size as 0.0067, is that value about wavelength? why 0.675?
I have explained my choices in the video, please have a look at the video.
@30:47 why did you set "max cell size"s "percentage of base" as 100?
This is the maximum cell size within the domain, which will be 1 meter. This is an acceptable value for the maximum cell size within a computational domain.
@33:24 why did you set "surface control2 -> percentage of base -> 86.4"? why not 100?
Please have a look at this video: ruclips.net/video/6qRPOqXgjNc/видео.html
@36:26 why did you set height of "freesurfacecoarse" block as 1m?
To cover the whole submarine body and at the same time to ensure a smooth mesh transition.
@40:21 you created a block to make another volumetric control around DARPA, how did you decide the dimensions of that block? and why its trimmer is isotropic? and why its percentage of base is 2.7?
I have explained this in the video.
@@CFD_Mojtaba Sir, thank you very much for your answers. All your videos are wonderful reference guides. Thank you so much for sharing your knowledge.
Thank you for this impressive tutorial, very interesting, but in 24.19 minutes, I made some calculations based on the equation given, i got m = 31.06 not 23? correct me if I'm wrong? Tq
Great tutorial! It was very helpful!
I have one question:
How do you determine the angle theta? (The angle between SUBOFF's travel direction and the crest of the waves )
Thank you for this comment. In order to find this angle, you need to first identify the position of the wave crests (at least two), then you can interpolate a line through thee crests, which consequently can be utilized to compute the angle between the SUBOFF and the propagating waves.
How can we identify the position of the wave crests@@CFD_Mojtaba
@@MohammedKhantheacademicianyou can export the solution data into a spreadsheet and then find the position of the wave crests using another code, such as MATLAB.
@@CFD_Mojtaba to get a solution, I must perform a simulation, to perform a simulation I must enter also specify wave length damping factor, to specify damping factor need to know the theta.
I don't know where I am missing something.
@@MohammedKhantheacademicianplease have a look at this paper: www.sciencedirect.com/science/article/pii/S0141118718303808
thank you very much and great explanation and really appreciated, could you share to me the simulation file and CAD for DARPA, and do you have the appendage DARPA CAD?, i would love to try to do it for my practice purposes and study. thank you.
Please send an email to this address mojtaba@lts.coppe.ufrj.br
Great! Thank you! Keep it up!
Hello, how can i dowload this program ?
Hi sir I'm doing a mini project on the wake analysis of underwater vehicles so please provide me with the geometry so tht I can do cfd analysis
The link which you provided to download the geometry is showing error, and more doubt can this be performed in ansys student version?
Dear shrivatsataddewadi8012,
You may need to change the geometry format to STEP, or any other popular formats.
Thank you for this tutorial, sir can you make the tutorial on air supported floating platform to find its heave response
Thank you for your suggestion. I will try to do this. Note that you probably need to consider that the fluid flow is compressible.
Sir, actually i model the background like you model it for buoy motion tutorials and for air-supported it is a box structure open at bottom but in starm ccm, I was unable to model the opening at the bottom, so I thought of assigning some boundary conditions to the bottom and sir i have a question how can i model air inside the box and tell me how i should model so that backgorund water should go inside it to compress air.what boudary condition i should assign for open part initially it is wall.@@CFD_Mojtaba
@@VikashKumaroe22m021maybe you dont need to model explicitly the air behvior. You can express this effect as an external force.
@@CFD_Mojtaba ok thank you sir and which boundary condition i should assign for bottom surface of box so that background water can go inside it,
Can you plz provide me your star ccm file in which you did all the work, for my reference
Dear Prateek Singh,
Please, send an email to this address: mojtaba@lts.coppe.ufrj.br
Respectfully,
Mojtaba Maali.
@@CFD_Mojtaba I just sent you an e-mail
@@CFD_Mojtaba I also sent you an email, looking forward to your reply.
@@CFD_Mojtaba Thank you for your tutorial. It is very helpful. And I also sent an email to you. Looking forward to your reply sir.
Very helpful!!
amazing
so good！！！！
I want to know how to calculate resistance without additional devices，
can you give me some advice or show me the paper address
thanks so much！
can you help me in my problem?
my vertual tank rotates when i started to run it
great!!!!!!!!!!