Free Engineering Simulation Tutorial - Opensource Software & Simulation Guides

You picked your turbulence model, you set your target y+ — but now your mesher is asking for a number in metres, and getting it wrong ruins the whole simulation. The first cell height is the single most important near-wall mesh parameter in CFD, and it must be reverse-solved from your target y+, the flow velocity and the fluid properties. This free Wall y+ First-Cell-Height Calculator does exactly that — it runs the full chain (Reynolds number → skin friction → wall shear stress → friction velocity → cell height) for both external and internal flows, giving you the exact wall spacing to build a correct boundary-layer mesh. Figure 1 y+ for cfd meshing analysis Table of Contents The First-Cell-Height Calculator What Is the First Cell Height? Why Reverse-Solve from y+? The Calculation Chain Skin-Friction Correlations Which y+ Should You Target? Worked Example First Cell Height vs Prism Layer Common Mistakes FAQ Th...

You set up a perfect mesh, chose k-ω SST, hit run — and your turbulence quietly dies before the flow even reaches the object. The cause is almost always the same: bad turbulence inlet boundary conditions. Two-equation models like k-ε and k-ω SST need starting values for turbulence at the inlet, but those values ( k , ε , ω ) are hard to guess directly. The trick every CFD engineer uses is to specify two intuitive quantities instead — turbulence intensity (I) and length scale (ℓ) — and convert them. This guide gives you a free, validated calculator that does exactly that, plus the theory behind every number. Figure 1. At a CFD inlet you specify turbulence intensity (I) and length scale (ℓ), and the solver converts them into k, ε and ω — the quantities the turbulence model actually solves. Table of Contents The Turbulence Inlet BC Calculator Why Turbulence Inlet Conditions Matter Turbulence Intensity (I) Turbulence Length Scale (ℓ) The Conv...

Before you run a single CFD simulation, one number decides almost everything: the Reynolds number. It tells you whether your flow is smooth and orderly (laminar) or chaotic and mixing (turbulent) — and that single distinction determines which turbulence model you choose, how fine your mesh must be, and whether your results will be right or hopelessly wrong. This guide gives you a free Reynolds number calculator (validated against textbook values), explains the formula in plain language, shows you how to pick the tricky characteristic length, and — importantly — explains exactly how the Reynolds number is used to set up a CFD simulation . Figure 1. The Reynolds number sorts every flow into laminar, transitional or turbulent. It is the ratio of inertial forces to viscous forces — the single most important dimensionless number in fluid mechanics. Table of Contents The Reynolds Number Calculator What Is the Reynolds Number? The Formula Explained Choo...