This document provides an overview of ZNTutor-CFD, a CFD tool for learning the basics of computational fluid dynamics (CFD). It describes the tool's philosophy of serving as a virtual fluid mechanics lab and introduces its two modes: Wizard mode and Interactive mode. Wizard mode allows users to solve predefined problems quickly with guidance, while Interactive mode allows users to define new geometries and problems. It then demonstrates Wizard mode through examples of a 1D shock tube problem and converging-diverging nozzle. Finally, it shows how to define and solve a problem in Interactive mode using the example of flow over an inclined ramp.

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Defense | Nuclear Power | Aerospace | Infrastructure | Industry
CFD tool for learning the basics of CFD
Abhishek Jain
abhishek@zeusnumerix.com
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 Grid2D Structured Create Init Block
 Input X = 1.0 and Y=0.4
 Divide the block in three parts
 Grid2D 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 Grid2D 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
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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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Result
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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

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Thank You!
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Questions?