# Questions tagged [fluid-dynamics]

The study of the properties of fluids and gases in motion

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### sign of slope ratio in limiter function

I'm studying Flux Limiters. I have the questions Is the slope $r_i$ allowed to be negative? If so, why is the region $r_i < 0$ not shown in the Sweby diagram at the bottom of that page? Thanks. ...
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### Any resource focusing on choosing the right SPH simulation parameters?

I am a software engineer with no prior experience in numerical and/or physical models (apart from very simple particle simulations). The last few weeks I've been trying to implement a 2D real-time SPH ...
1 vote
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### Applicability of 1/7 power law for turbulent flow

I am looking to do a CFD study of a turbulent flow through a pipe. I know the average velocity from the flow rate so I decided to use the popular 1/7th power law model for the fully developed ...
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### Need help with adaptive meshing code

I am trying to understand adaptive meshing and is using this code (https://github.com/esquivas/amr1d) as a reference. However, there is no documentation for it and thus, it is hard for me to ...
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1 vote
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### Bachelor thesis going out of hand, need help [closed]

I am currently working on my bachelor thesis, which aims to enhance the multigrid preconditioned conjugate gradient algorithm proposed by Tatebe in 1993 using Deep Learning. Currently, I am ...
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### How to calculate the force of solid applied by fluid? Using finite difference method, DNS, staggered grid, SIMPLE algorithm, immersive boundary

Problem I am using finite difference method to solve classic problem of flow around cylinder, for validation of my group's immersive boundary method. The common way to validate numerical method is ...
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### How do we implement the balance of stress on interface in ALE FSI method?

""we aim for a consistent variational-monolithic coupling scheme in which we need all equations defined in the same domain; therefore, $\mathrm{ALE}_{f x}$ was introduced. In variational ...
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### Exact Riemann Solver for Multi-Component 1D Euler Model

I am concerned looking for an exact Riemann solver for compressible 1D multi-component Euler equations, supplied with the ideal gases equation of state and under the assumptions: Mechanical ...
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### How to address the element face adjacent to boundaries when the finite difference method and marker-and-cell scheme are used to solve the Stokes flow?

The Stokes equations are $$-\Delta \mathbf u + \nabla p = f \text{, in }\Omega,$$ and $$-\nabla \cdot \mathbf u = g, \text{ in } \Omega$$ where $\mathbf u = \left( u, v \right)$ is the flow ...
1 vote
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### How can we use the two boundary conditions for the Taylor-Maccoll Equations for Cone Shock Waves?

The Taylor-Maccoll equations below govern the gas dynamics around a supersonic, axially oriented cone. Using the notation from Anderson's Fundamentals of Aerodynamics, which uses a dimensionless ...
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### Why do we use modified pressure in incompressible multiphase solvers with gravity?

The context of my question is two-phase incompressible solvers such as interFoam in OpenFOAM, but I have seen this trick used ...
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### Fluent Induced Drag Aerofoil Convergence Error

I am currently modelling what happens, to lift induced drag, when you apply washout to a wing (Twist). However I have a few issues the drag values I calculate are into the 1000s the drag values ...
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### Energy potential involvign pressure and viscoscity?

Making a really long explanation short. I am looking for an energy density function for an incompressible isotropic fluid that involves both viscoscity and pressure. The reason is, there is a way to ...
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### Solving a minimization problem without flattening inputs?

I am reading this paper on improving time steps for solving simulation problems: https://www.math.ucla.edu/~jteran/papers/GSSJT15.pdf The authors developed this energy function: E(x) = \frac{1}{2\...
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### Projection (or fractional-step) methods Vs coupled method for incompressible Navier-Stokes

My question is in the context of the finite element method. Incompressible Navier-Stokes equations can be solved using the coupled method or projection/fractional step methods. Each method has its ...
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### How do the navier stoke equations model materials who "forget" their original form?

Sorry for the screenshot but I don't want to try to format this on latex: We have this annotation of the Navier-Stokes equations: I am particularly puzzled by the viscosity/stress term. For an ...
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### Adding stability to MPM simulation?

I am writing a 2D implementation of MLS-MPM, I have fluids working perfetly fine, solids technically work as well, at low time steps. This is the fluid simulation at a large time step: https://i....
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### SPH example codes for solving differential equations

I'm quite new to the smoothed particle hydrodynamics method, so I'm trying to find Matlab or Python code to help me understand it. Specifically, I want to know how to solve the one-dimensional ...
1 vote
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### How to calculate the reynolds number for airborne wind energy system?

I am asking for some help on how to calculate the reynolds number for an AWES. I know the formula of Re=rhovl/viscosity. I have selected the air foil as Clark y with chord length 3.72m (which will be ...
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### discrete definition of curl $\nabla \times \vec{A}$ on a 3D grid?

I have the data for 3D vector field $\vec{A}$ (with components $\vec{A_1}$, $\vec{A_2}$ and $\vec{A_3}$) sampled on a 3D grid with integer indices i, j and k. Assuming that only the third component \$\...
1 vote
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### Fortran - Lid-Driven Cavity Boundary Conditions Error when using SIMPLE method

I am studying Numerical Methods for incompressible flows. part of the tasks is to model the lid driven cavity problem in 2D using the SIMPLE method. I have been provided with Fortran code that is ...
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