Introduction to ZNTutor-CFD

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Defense | Nuclear Power | Aerospace | Infrastructure | Industry

CFD tool for learning the basics of CFD

Abhishek [email protected]

ZNTutor-CFD: An Introduction

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Overview of Presentation

Philosophy

Wizard mode

1D Shock tube problem

Converging-Diverging Nozzle

Interactive mode

Flow over a ramp

Analysis

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Philosophy

ZNTutor-CFD™ is aimed at introducing students and beginner engineers to CFD

It serves as a virtual fluid mechanics lab

The purpose is to give a feel of CFD but not solving industrial problems

It takes you through the whole CFD process

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The Two Modes

Wizard Mode

Pre-defined problems from fluid mechanics text books

Problems can be solved in few minutes

At all steps guidance is given to the user

Interactive Mode

Learn to define a problem

Make new geometries for simulation

Inbuilt geometric modeler and post-processor

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WIZARD MODE

Functioning of wizard mode

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Wizard Mode: GUI

Menu Bar

Problem stage

Problem selection

Commands and feedback line

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1D Shock Tube Problem

Shock tube problem is defined as sudden change of properties in space

Define Numerical Schemes – to inform participants about the merits and demerits of each scheme

Select Solver Control – define the domain, CFL, time step

Define Initial Condition – Physical properties like pressure, density, velocity

View Solution – shows the actual solution in red and the simulation result in green

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GUI

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Result: Analytical & Computed

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2D WIZARD

Example problem in 2D wizard

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The 2D Wizard

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The 2D Wizard

Define problem – choose from a list of problems

Define geometry – the menu gives a description of geometry and in some cases parameters can be changed

Define grid – problems give choice of structured and unstructured grid

Select solver control – choose solution algorithm, accuracy etc

Define flow condition – supply the flow conditions at which the problem is to be solved

View solution – choose initial conditions, number of iterations, time marching etc

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Final Grid

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Solution

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INTERACTIVE MODE

To define and solve a problem in interactive mode

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Problem Definition

Problem definition has to be thought of by user and then appropriate tools must be chosen to create geometry

Here we chose flow over an inclined ramp

Figure show the problem statement

Expected an oblique shock on the ramp

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Supersonic inflow

Outflow

1 m

0.3 m

0.5 m

0.04 m

0.36 m

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Creation of Topology & Grid

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Create a domain

Menu Grid2D Structured Create Init Block

Input X = 1.0 and Y=0.4

Divide the block in three parts

Grid2D Structured Create Input Values

Input – X = 0.5, Y=0.1

Input – X = 0.3, Y=0.2

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Complete Geometry

We can complete the geometry the moving the two vertex in bottom right upward

Select the vertex to move up

Use Grid 2D Structured Edit Edit Operation

Input X = 0, Y=0.04, Z=0

Select other vertex and repeat the same

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Grid generated

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BCs and Clustering

Clustering means to increase the density in a location where the gradients are supposed to be high

Use Grid2D Structured Clustering All Blocks

Input: One side, 17 points, 0.4%

Boundary conditions

Select leftmost edge and assign inflow

Boundary Condition Define as Inflow

Similarly define rightmost edge as outflow

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Simulation

Fluid Model

Compressible flow; 2nd order accurate in space

Flow Conditions

Freestream Mach – 3.0, pressure and temperature

Execution Setup

Time marching – LOCAL – Every cell marches with own speed; CFL number

Desired residue fall for convergence; Number of iterations for convergence and display after every iteration

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Analysis

We measure the ramp angle – 11.3 degree

Shock angle obtained ~ 28 degree

Theoretical angle – 28.5 degree

Good matching between theoretical and experiment

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Ref: Jet propulsion laboratory

Introduction to ZNTutor-CFD

Engineering

Transcript of Introduction to ZNTutor-CFD