2018年5月1日 · There can never be a last word in regard to the axioms of any physical theory. All we can ask of them is that they lead to conclusions in agreement with observation. Sooner or later more refined observations will find the weak point in any set of physical axioms. Nature is far too complicated to be completely described in a few equations. - J.L. Synge (1938) …

The formulas used are give in CFD-Wiki here.The Schlichting skin-friction formula, as desribed here (equation 21.16 footnote in Schlichting), is used to estimate the local skin-friction for a turbulent boundary layer on a smooth flat plate.

Y+ Wall Distance Estimation; A y+ wall distance estimation script provided by CFD Online. Uses the free-stream velocity and gas-data to estimate the wall distance needed to obtain a desired y+ value at a certain boundary layer length. This is one of those wonderful little tools that saves you from learning a formula! Viscous Grid Spacing Calculator

2020年2月28日 · \(y+\) is the dimensionless wall distance that is helpful in determining the thickness of the first cell away from the wall boundary for the given flow parameters. Equation (1) from the forum article above states: $$ y+ = y \frac{u_t}{\nu} $$ where, \(u_t\) is the friction velocity \(y\) is the absolute distance from the wall

Y+ Estimation Estimates the wall distance needed to obtain a desired Y+ value. Turbulence Properties, Conversions & Boundary Estimations Use the tools here to convert and estimate turbulent properties at boundaries.

2005年10月23日 · The distance is usually measured in the dimensionless wall units, y+ (≡ ρuτy/µ), or y*. Note that y+ and y* have comparable values when the first cell is placed in the log-layer but are different by C_µ^(1/4), i.e. ≈ 0.5. «

When meshing it is often useful to be able to estimate the wall-distance needed to obtain a certain Y+ value. To estimate this you can do the following: 1. Compute the Re number: 2. Estimate the skin friction using one of the formulas given here, for example, using the Schlichting skin-friction correlation: 3. Compute the Wall shear stress: 4.

In the case of y+, it is a scaled y-coordinate in the layer closest to the wall. The boundary layer velocity profile turns out to be linear with y+ in this innermost layer until y+ reaches some matching value with the next layer. Similar criteria is used in the CFD community to select grid point spacing nearest the wall. Hope that helps.

2013年4月17日 · Ideally, you should have a y+ smaller than 1 on all your surface. But there is no need to go to 1e-3 ! Be careful, the size of your first cell must correspond to your turbulence model. For example a RAS k-omega SST requires a y+ smaller than 1 but a k-epsilon standard requires a y+ between 30 and 60.

2018年5月8日 · \\underline{\\textbf{Applying y+ through meshing in SimScale}} SimScale allows you to perform “Inflate Boundary Layers” on to the geometry surface as seen below. This option can be applied to a surface where the layers will then be inflated from the surface to allow you to control the y+ of the mesh. You then need to first determine your desired y+ depending on …