The study of the properties of fluids and gases in motion

learn more… | top users | synonyms (1)

0
votes
0answers
21 views

Convected 2nd order tensor in component form [migrated]

I have a convected second order tensor that I'd like to write in component form. $\frac{D\mathbf{a}}{D t} = \frac{\partial \mathbf{a}}{\partial t} + \mathbf{v}\cdot\nabla\mathbf{a}$, where ...
2
votes
0answers
42 views

Euler Equation Eigensystem with Gravity in the Energy Flux

I am modifying a conservative form of the Euler equations with gravity in the energy flux (see previous question: Energy Conservation in Conservation Laws with Source Terms) for use in a Riemann ...
0
votes
0answers
17 views

LBM for thermal anlysis

Can Lattice-Boltzmann methods be used for thermal analysis of radiation or conduction? (Hints for papers and libraries are highly appreciated.)
-2
votes
0answers
34 views

Can we take transport equation of imaginary quantity? [on hold]

The question is asked in Physics StackExchange and it didn't turn out to be fruitful so I am posting it here. In the RANS equation we approximate the nonlinear fluctuating terms to eddy viscosity ...
3
votes
2answers
99 views

How to set up a shock tube problem such that the solution includes a shock with a specified Mach number

One of the famous and convenient test cases for shock wave modeling is the 1D Sod's shock tube. This is a Riemann problem for the compressible Euler equations of gas dynamics. The initial set up has ...
5
votes
3answers
109 views

Test Case with Known Solution for 3D Navier Stokes Equations

Is there a test case for 3D incompressible Navier Stokes Equations like the Taylor vortex in two dimensions? I know, I can easily construct 3D manufactured solutions but I would like to have ...
1
vote
2answers
70 views

Nondimensional gas constants

I am doing a nondimensional Navier-Stokes simulation, but it's not exactly clear what values to use for the various gas constants: $R$, $C_v$, and $C_p$. Obviously, once I know one of these and ...
1
vote
0answers
22 views

Compute drag force on a mesh in SU2 CFD (beginner) [closed]

I am a complete beginner in computational fluid dynamics. I have a 3D mesh in Blender representing the object I would like to do my tests on. I can export it in (I think) any useful format for 3D. I ...
0
votes
0answers
12 views

Convergence criterion for overset grids

If there are two overset grids, how do you decide whether convergence is reached or not? What I did was, after interpolating from one grid to another, I check the rms of conservative variables and if ...
0
votes
0answers
26 views

SPH fluid simulation steady state

I am trying to implement a fluid simulation using SPH, based on these paper, being the latter the one with the algorithm. I went through the math and try it out with some values just to check whether ...
0
votes
0answers
24 views

coriolis force in atmospheric modeling [migrated]

The coriolis force is not a real force, but depending on the reference system and how it does refer to an inertial system. Could this coriolis force as widely used in atmospheric/climate modeling be ...
4
votes
2answers
250 views

What are the differences between CFD simulations and realistic ocean/atmosphere model simulations?

The field of computational fluid dynamics (CFD) is dedicated to solving the Navier-Stokes equations (or some simplification of them). A subset of CFD, ocean and atmospheric models numerically solve ...
3
votes
1answer
65 views

Deriving entropy function and entropy flux for a system of equations

I've been reading up on the concept of entropy as a useful way of developing a natural residual for a system of equations. For example, the entropy function for compressible Navier-Stokes is ...
2
votes
1answer
123 views

Energy Conservation in Conservation Laws with Source Terms

I'm wondering if anyone can help me understand energy conservation when using conservation law methods (i.e. Riemann solver, High-Resolution Wave-Propagation Methods) with the addition of source ...
1
vote
1answer
129 views

Patankar's algorithms for Numerical Heat Transfer and Fluid Flow

I am looking for the algorithm of Patankar (for example, SIMPLE, SIMPLER, SIMPLEC and PISO) written in Fortran for the simulation of heat transfer and fluid flow.
0
votes
1answer
58 views

jump conditions for Poisson/Darcy equation in primal form versus mixed form

Consider the Darcy equation, $$\mathbf{v} + \dfrac{k}{\mu_0}\nabla p = \mathbf{f} \\ \mathrm{div}\; \mathbf{v} = 0$$ If the coefficient $k$ is piecewise constant across an interface $\Gamma$ in the ...
5
votes
1answer
94 views

Is there a jump condition for this PDE? ( Brinkman model , piecewise constant permeability)

The Brinkman equations for steady flow of an incompressible fluid through rigid porous solid are: $-\dfrac{\mu_0}{k}\mathbf{v} - \mathrm{grad}p + \mu_0 \Delta \mathbf{v} =0$ and ...
2
votes
2answers
76 views

Simulating interaction of Smart Fluids with Solids

Is it possible to simulate interaction of Smart Fluids with Solids? Is there a software capable of doing so? What I Know: The two software that I know of are Autodesk Simulation Mechanical and ...
2
votes
0answers
64 views

How to get proper parameters of SPH simulation?

I'm implementing basic fluid flow simulator using SPH method basing on e.g. https://www10.informatik.uni-erlangen.de/Publications/Theses/2010/Staubach_BA10.pdf. So far I've implemented: uniform ...
4
votes
2answers
146 views

Projection Method: Boundary condition on intermediate velocity field

I'm trying to solve variable density and viscosity Navier-Stokes equation using lagged pressure projection method. I'm solving for cavity problem as a test case now (once I get projection right, I ...
0
votes
1answer
52 views

FEM with soil slope

I what to calculate displacements, stress and strain in a soil slope with a FEM script. The slope moves like a laminar flow. Can you suggest me some bibliography on this problem? I've already look on ...
3
votes
1answer
138 views

Finite Elements Weak Formulation generalization

I am struggling with an equation that represents the Weak form of Galerkin method: $ \phi^{T}F(\textbf{u})\sim \int_{\Omega}^{ } \phi.f_{0}(\mathit{u},\nabla \mathit{u}) + ...
2
votes
1answer
139 views

Organizing a CFD program written in python

I've spent some time writing a spectral element solver aimed at solving fluid flow problems concerning the motion of self-propelled bodies. I've gotten to the point where the code has grown long ...
4
votes
3answers
153 views

vector PDEs on manifolds

What are the subtleties involved in solving vector PDEs on manifolds? Can someone suggest a reference summarizing the problems involved? Specifically I want to solve a vector Helmholtz equation with ...
2
votes
2answers
190 views

CFD absractions in Modern Fortran

I'm a novice in object-oriented programming, but this design technique seems very interesting for me. I have a Fortran 90 CFD package , not very complex, but it is already very hard to maintain and to ...
0
votes
1answer
134 views

MPI_ERR_TRUNCATE appears for no understandable reason

I am developing some parallel CFD code using Fortran 90 and OpenMPI. The processes are structured into two groups such that half perform a certain type of calculations (let's say Velocity, Pressure ...
1
vote
1answer
75 views

Importance of change the Time Step Value for the Accuracy of a Transient CFD Simulation

I have a transient simulation for a case from 0 to 3 sec , actually i interest the solutions on time range from 2 to 3 sec , as my velocity and mesh size , my time step should be 0.0000000001 sec , my ...
3
votes
2answers
148 views

C - OpenMP, MPI, Serial Program

I'm part of a Computational Science course and come from a non-programming background, so please forgive me my ignorance. I'm working on a set of code in C to numerically solve the Navier Stokes ...
0
votes
0answers
25 views

Tecplot Span-Wise Loading Visualization

all. I have data from a CFD simulation for a wing, and I need to obtain a visualization of the span-wise load distribution. I'm attempting to do this using Tecplot. I've tried using 'slices' and ...
1
vote
1answer
111 views

Type of Navier-Stokes equation

What type equation Navier-Stokes is: Elliptic, parabolic, or hyperbolic? Should it give always the same answer no matter what is the initial condition? How these statements could be proved?
0
votes
1answer
55 views

Regarding streaming operator in Lattice Gas Automata

The classical streaming operator used in FHP lattice gas automata is this: $$n_i(r - c_i, t + 1) = n_i(r, t)$$ However if you think in terms of the streaming itself, it should be something like ...
2
votes
2answers
126 views

Solving Stokes flow with walls using Oseen tensor

Introduction I've developed a code to solve for generalised, incompressible 2D Stokes flow $\eta \nabla^2 \mathbf{v} - \nabla p + \mathbf{S} = 0$ $\nabla . \mathbf{v} = 0$ where $\mathbf{S}$ can ...
2
votes
3answers
139 views

How to get discretization coefficients of matrix A in Finite Volume Method (FVM)?

First we have Discretization of the Transport Equation $$ \frac{\partial \rho \phi}{\partial t} + \nabla(\rho U \phi) - \nabla (\rho \Gamma_\phi \nabla \phi) = S_\phi (\phi) $$ In Finite Volume ...
0
votes
4answers
148 views

What scale problem can be simulated on an PC using Smooth Particle Hydrodynamics?

I want to simulate tidal features in a large body of water using was smooth particle hydrodynamics. For a system composed of an incompressible fluid, what general scale of problem can be tackled with ...
4
votes
2answers
133 views

What makes turbomachinery so special in CFD

As my experience with CFD grows, I start to gain the feeling that turbomacinery is kind of special in CFD: there are special tools tailor for it. For example, ANSYS has TurboGrid or Vista TF for ...
11
votes
2answers
210 views

Do black-box preconditioners for matrix-free methods exist?

Jacobian-Free Newton-Krylov (JFNK) methods, and Krylov methods in general, can be very useful because they don't require explicit storage or construction of a matrix, only the results of matrix-vector ...
3
votes
1answer
224 views

Comparison of Lattice Boltzmann Method vs Traditional Navier-Stokes based Methods

I have a choice of two options, analysing and implementing Lattice Boltzmann methods or traditional Navier Stokes based methods. I'm a CFD newbie and I have a rough idea (though not rigorous enough to ...
1
vote
1answer
100 views

Is it possible to simulate fluid dynamics in a time-based and deterministic manner?

The Problem Domain I have a number of network-connected PCs. I want to be able to simulate and replicate the same simple fluid dynamics simulation (E.g. Navier-Stokes), in real-time, between them. ...
1
vote
1answer
152 views

Moving airfoil boundary conditions

I am trying to simulate a moving airfoil with constant speed (Mach=0.755, aoa=1.25). I solve Euler equations with Roe's method. I have two boundary conditions: Farfield Slip wall (airfoil) For all ...
1
vote
2answers
148 views

Computing Kolmogorov/Energy spectrum for turbulent boundary layer

Previously, I have calculated energy spectrum for 3D DNS data obtained for isotropic turbulence which is equally spaced in all three directions and then to compute the energy spectrum, one performs ...
0
votes
2answers
93 views

WENO reconstruction of flux involving derivative terms

I have a set of modified compressible Euler equations that I would like to solve using a WENO method. The issue is that the modified flux function involves derivative and filtering terms and I'm not ...
0
votes
1answer
54 views

How to model waterflow when only a couple of sample points available

Figure below depicts a cross section of a creek for which I am trying to measure the water flow for that section. What we have as inputs are a bunch of sample points on the river. For each sample ...
0
votes
1answer
180 views

Dual time stepping for fluid dynamics

I'm attempting to implement the Weiss and Smith preconditioner in an existing finite volume code and I am struggling with the idea of dual time stepping. My inner time steps are predictor-corrector, ...
1
vote
0answers
99 views

High-order continuous Galerkin Navier-Stokes solver in deal.II

I looked at the list of publications related to deal.II, but it seems that when it comes to Navier-Stokes equations, everyone speaks about Discontinuous Galerkin solver in their papers. I know there's ...
1
vote
1answer
190 views

Euler's equations 1d for pipe, Inlet boundary conditions

$\def\rmin{{\mathrm{in}}}$ $\def\l{\left}\def\r{\right}$ $\def\tagl#1{\tag{#1}\label{#1}}$ I am using the one-dimensional finite volume method to calculate the air flow in some tube. For subsonic ...
1
vote
0answers
51 views

Turbulence: Suggest research papers similar to this experiment

I am trying to find the effect on turbulence characteristics when flow passes through a converging section. For this experiment I will use a PIV system to gather data about the flow. However, I could ...
3
votes
1answer
125 views

Euler's equations for a tube with varying cross-section

$\def\pd{\partial}$ $\def\l{\left}\def\r{\right}$ $\def\mdot{{\dot{m}}}$ $\def\eps{\varepsilon}$ Consider a tube with longitudinal coordinate $x$ from $0$ to $l$ and varying cross-section $A(x)$. ...
2
votes
1answer
104 views

2d pseudo-spectral turbulence simulation with random initial velocities

I am trying to write a 2d pseudo-spectral DNS code with random initial velocities. This is kind of a classic simulation where the very tiny vortices group together forming larger and larger vortices ...
0
votes
0answers
44 views

Numerical strategy to detect the point of detachment over the wall of cylinder in the simulation of unsteady flow over circular cylinder

I am working on unsteady simulation of flow over circular cylinder where we get Kármán vortex street. Kármán vortex street is a repeating pattern of swirling vortices caused by the unsteady separation ...
1
vote
1answer
52 views

“boundary” vs “interface”?

I am working with biofilm and there are many documents talking about boudary conditions while others talks about interface or both of boundary and interface. So, boundary and interface are the same ...