Design of high energy pump impellers to avoid cavitation instabilities and demage

Hello All,

Currently, I am using a licensed version of ANSYS 2019 R2 along with CHEMKIN Pro Package. 

I was trying to import a CHEMKIN reaction mechanism file (.inp) that is included in CHEMKIN Package in the model fuel library. The name of the file is NaturalGas_Methane_CHEM_MFL_2018.

When I use the same mechanism in Chemkin simulation, it works well. But, as I wanted to import it Fluent, it failed with an error message - Failed to import CHEMKIN mechanism.

Could you please let me know how to solve this problem?

Thank you

Hello,

I constantly submit parallel jobs in a shared HPC cluster for my OpenFOAM flow simulations and like everyone else, I have to decide how many cores I need. Our cluster runs constantly over head and my jobs often wait in the queue. I know that it heavily depends on geometry, solver and system specifications, but are there any ways to make a rough estimate of "optimum number of cores" before losing speedup, based on the number of cells and -be it OpenFOAM's- solver?

Thanks in advance,

Huseyin

Why shouldn't we worry about CFL (courant) number for URANS numerical simulations?

For computational analysis of turbomachines

Generally wear occurs on the bearing surface due to the phenomenon of cavitation. I am planning to do Phd in this topic. So i need a test rig to measure cavitation.

Cavitation is the formation of vapour cavities in a liquid – i.e. small liquid-free zones ("bubbles" or "voids") – that are the consequence of forces acting upon the liquid. It usually occurs when a liquid is subjected to rapid changes of pressure that cause the formation of cavities where the pressure is relatively low. When subjected to higher pressure, the voids implode and can generate an intense shock wave

The SnO₂ films that I have sprayed always have powder formation whenever at high temperature(>320℃) or low temperature(room temperature~150℃). The films are not smooth and like to be formed by many small pieces. Which parameters should I adjust and how should I try? Thank you very much.

I am currently looking for ideas for my thesis (Bachelor of Mechanical Engineering) and I am trying to see what possible areas within the 3D printing community would possibly be suitable. Any suggestions would really be appreciated!

Edit: one possibly idea is something regarding using 3D printing to help during a pandemic?

All of these problems are expressed through mathematical partial differential equations (PDE’s). While today’s computers can’t single-handedly solve PDE’s, they are equipped to solve matrix equations. These matrix equations can be linear or nonlinear. In most structural problems, the nonlinear equations fall into 3 categories:

· Material Nonlinearity: Where deformations and strains are large (i.e., polymer materials)

· Geometric Nonlinearity: Where strains are small, but rotations are large (i.e., thin structures)

· Boundary Nonlinearity: Due to non-linearity of boundary conditions, (i.e., contact problems)

In linear problems, the PDE’s reduce to a matrix equation as:

and for non-linear static problems as:

For dynamic problems, the matrix equations come down to:

where (.‘) represents the derivative.

One method of solving for the unknowns {x} is through matrix inversion (or equivalent processes). This is known as an implicit analysis. When the problem is nonlinear, the solution is obtained in a number of steps and the solution for the current step is based on the solution from the previous step. For large models, inverting the matrix is highly expensive and will require advanced iterative solvers (over standard direct solvers). Sometimes, this is also known as the backward Euler integration scheme. These solutions are unconditionally stable and facilitate larger time steps. Despite this advantage, the implicit methods can be extremely time-consuming when solving dynamic and nonlinear problems.

Explicit analyses aim to solve for acceleration (or otherwise {x´´}). In most cases, the mass matrix is considered as “lumped” and thus a diagonal matrix. Inversion of a diagonal matrix is straightforward and includes inversion of the terms on the diagonal only. Once the accelerations are calculated at the nth step, the velocity at n+1/2 step and displacement at n+1 step are calculated accordingly. In these calculations, the scheme is not unconditionally stable and thus smaller time steps are required. To be more precise, the time step in an explicit finite element analysis must be less than the Courant time step (i.e., the time taken by a sound wave to travel across an element) while implicit analyses have no such limitations.

The implicit method should be used when the events are much slower and the effects of strain rates are minimal. Once the growth of stress as a function of strain can be established, these can be analyzed using implicit methods. In this case, one can consider a static equilibrium such that:

This covers many of the most common engineering problems.