请问关于附加质量力的求解 我应该看OF哪个求解器的算例呢？

[迟铁]

最近做了wagner的楔形物如水的模拟，然后做了球鼻艏入水的二维模拟，需要求一下附加质量力，看了一些文章，也在openfoam里找了下，不知道用哪个求解器。我就看了下potentialFoam那个cylinder算例，那个能求吗。

[迟铁]

摘自CFDonline的原文：
I want to use potentialFoam to find added mass of a cylinder. It is well known this geometry has an added mass equal to the displaced fluid (rhopir^2*L).

Frank White, Fluid Mechanics, writes: "According to potential theory, mh depends only on the shape and direction of motion and can be computed by summing the total kinetic energy of the fluid relative to the body and setting this equal to an equivalent body energy: KEfluid=integral(0.5dmVrel^2)=0.5mhU^2)", where mh is the added mass. I interpret this for a numeric solver so that mh=sum(dmVrel^2)/U^2=sum(dVolumerho*Vrel^2)/U^2.

I have set up a model in OpenFOAM similarily to the example "Flow around a cylinder". The biggest difference being that the uppper and lower boundaries are set to walls with slip boundary condition, to enable uniform flow over the geometry. I have used 10 non-orthogonal corrector steps, to get correct results. I use a fluid volume that is about 4 diameters in the flow direction and 3 diameters across, use snappyHexMesh and extrudeMesh to get a nice mesh with boundary layers around the cylinder.

After solving with potentialFoam I extract the cell volume of each cell with "postProcess -func writeCellVolumes" and use an octave script to extract the cellvolume and velocity vectors from the OpenFOAM U and V files and calculate the added mass through a loop:

Code:

for i=1:L
Urel=U(i,:)-Uinit;
Urelsq=Urel.^2;
dm=rhoV(i);
mVsqtot=mVsqtot+dmUrelsq;
end
madd=mVsqtot./Uinit.^2;

where Uinit is the input flow, a vector with 1 m/s in the X direction, rho is hardcoded to 1000 kg/m^3 (water) and mVsqtot is an accumulator for the sum of dm*Vrel^2.

Unfortunately this does not give me correct result of 2.86 kg for a cylinder with radius of 30.165 mm, length 1 m, but rather close to half of that, 1.4361 kg. What am I doing wrong? Is it correct that the viscosity set is neglected with potentialFoam, but what density is used?

potentialFoam能求附加质量吗

[迟铁]

找到了个文献 http://html.rhhz.net/BJHKHTDXXBZRB/20160423.htm#R-19
差不多懂了

[迟铁]

想了下应该不是simpleFoam,因为并不是稳态，附加质量是和惯性有关，即加速度，那么就不是稳态，所以应该是pimple或者piso求解器

[迟铁]

附加质量-lamada

合力Fsum=(mass+lamada)*acceleration

lamada=(P*S)/g-m

[迟铁]

最后留两个Hess-smith方法求added mass的文献

1. The added mass coefficient computation of sphere,ellipsoid and marine propellers using Boundary Element Method. Hassan Ghassemi,Ehsan Yari.2011
   2.Calculation of added mass for underwater vehicles Based on FVM. Lihua SONG.2016

[李东岳]

不明觉厉 不明觉厉
楼主好人 感谢分享

[迟铁]

@东岳 东岳老师，你们都没算过附加质量吗。。

[李东岳]

木 不太懂你玩的是啥呢

[迟铁]

就是研究楔形物入水的附加质量啊

[wuyukai]

楼主搞定了吗，我最近分析一个圆柱加速运动，也想计算一下其附加质量力