CFD Analysis on Gulfstream G550 Nose Landing Gear

Innovation Intelligence®

7th European ATC

CFD analysis on Gulfstream G550 nose

landing gear

Dr. Konias A. Fotis

June 24-26, 2014 | Munich, Germany

Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.

Overview

• Introduction

• Problem description

• Geometry preparation

• Meshing

• Results – Validation

• Conclusions


Introduction

• Aerodynamics computational analysis for Gulfstream 550 nose landing gear

model with

partially-dressed, cavity-closed

Galerkin/Least-Square (GLS) finite element methodology

Objectives

Full representation of the flow

Results comparison against

experimental for validation

Software capabilities

presentation


Problem description

• 1/4-scale high-fidelity replica of a Gulfstream G550 nose landing gear

Model height = 449mm

Wheels diameter = 137mm

• Experimental data from closed-wall Basic Aerodynamic Research Tunnel (BART)

at NASA Langley Research Center (LaRC)

Test area dimensions:

H 700mm x W 1000mm x L 3000mm

700m

m


Flow conditions

• Incompressible air flow

Mach = 0.166 => Uinlet = 56.6 m/sec

Reynolds = 73,000 (based on the diameter of the shock strut l = 0.01905m)

Total Pressure inlet = 101,464 N/m2 Dynamic viscosity= 1.85313e-5 kg/m·s

Temperature = 23.28 oC Density of air = 1.25 kg/m3

Static Pressure outlet = 99,241 N/m2

Turbulence viscosity ratio = 1.0 => Eddy viscosity inlet = 1.482504e-005 m2/sec


Software used

v12 for geometry clean-up and meshing

v12 for pre-processing

v12 for processing

v12 for post-processing


Geometry clean-up

• IGS file geometry import

• Surfaces organized in different components

Surfaces grouping according to deferent parts

• Removal of redundant surfaces and geometries

Only external shell surfaces are needed

• Detect and repair of free edges

Formation of watertight model

• Repair of distorted geometries

• Minor geometry alterations

1st Option: Addition of missing joint connections

2nd Option: Closure of small gaps and proximities


Surface organize and removal

redundant

surfaces

Surfaces

grouped by

part


Repair of free edges and formation of watertight model


Repair of distorted geometries


Minor geometry alterations

• 1st Option : Addition of missing joint connections


Minor geometry alterations

• 2nd Option : Closure of small gaps and proximities


Meshing configuration

• 2D triangular surface mesh

2 cases, 1 for each geometry option

The same base configurations for all cases

2D automesh / surface deviation (before scale)

Refinement at closed volume proximities, narrow passages and corners

Coarser mesh for wind tunnel’s walls

Approximately 990,000 surface elements

• 3D tetrahedral mesh

3 cases of different first element height

Estimated Y+ <1 Approximately 78 million elements in total

>> Y+ <5 >> 60 million >>

>> Y+ <100 >> 40 million >>

Multiple groups of Boundary Layers for every case

3 Refinement boxes for core elements

upstream, around and downstream of geometry

Same core mesh configurations for all cases


2D Surface mesh details


Proximity and narrow openings refinement


2D Meshing in small gaps

1st Geometry option 2nd Geometry option


3D Tetrahedral mesh overview


Boundary Layers – Estimated Y+ at same spot

Y+ < 100

First height = 0.25mm

Growth rate = 1.2

No of layers = 6

Y+ < 5


Growth rate = 1.2 / 1.4 / 1.5

No of layers = 6 / 5 / 5

Y+ < 1


Growth rate = 1.2 / 1.3 / 1.4 / 1.5

No of layers = 6 / 6 / 5 / 5


Boundary layer details

Dynamic BL reduction

Y+ < 100

Y+ < 100

Y+ < 5

Y+ < 5

Dynamic BL reduction


Summary of mesh models

• 4 different case were studied in total

1) Estimated

2nd geometry option with closed small gaps and proximities

3 groups of Boundary layers in total, across whole model

2) Estimated

1st geometry option with no geometry alterations


3) Estimated



4) Estimated




AcuConsole pre-processing setup

• Preliminary 1st stage transient simulation, to wash out initial solutions

Problem Description

Analysis type: Transient

Turbulence equation: Spalart Allmaras

Auto Solution Strategy

Max time steps: 600

Initial time increment: 0.0001 sec

Nodal Output

Solution projected as Nodal Initial Condition for 2nd stage

• Main 2nd stage transient simulation, for final results

Problem Description

Analysis type: Transient

Turbulence equation: Detached Eddy Simulation

Auto Solution Strategy

Max time steps: 20,000

Initial time increment: 5e-006 sec

Nodal and Running Average Output

Nodal Initial Condition from 1st stage


AcuConsole boundary conditions setup

• Problem description

Analysis type : Transient

Flow equations : Navier Stokes

Abs. Pressure Offset = 0 Pa

Surface name BC Conditions

Inlet

Type: Inflow

X velocity = 56.6 m/sec

Eddy visc. = 1.482504e-5 m2/s

Outlet Type: Outflow

Pressure: 0.0 N/m2

Wind Tunnel Slip walls

All surfaces Non-slip walls

Inlet Non-slip

Floor

Outlet

Model surfaces

Wind Tunnel


Surfaces Y+ results


Average Velocity magnitude at center line plane

(Y=0m)

Y+ < 5 No gaps closed

Y+ < 100

Y+ < 5

Y+ < 1


Average Velocity magnitude at wheel axis plane

(Z=0.381m)

Y+ < 100 Y+ < 1

Y+ < 5 Y+ < 5 No gaps closed


Ave Velocity vectors at wheel axis plane (Z=0.381m)

Y+ < 100 Y+ < 1


Comparison with experiment: avg z-vorticity at wheel

axis (Z=0.381m)

Y+ < 100

Y+ < 1

Y+ < 5



Comparison with experiment: avg X velocity at wheel

axis (Z=0.381m)

Y+ < 1

Y+ < 5


Y+ < 100


Comparison with experiment: Cp around wheel


Conclusions and references

• Conclusions

• Strong available tools for a very good representation of the flow

• Overall good agreement with experimental results

• Good mesh sensitivity analysis

• References

1. Hughes T., Franca L., Hulbert G., A new finite element formulation for computational fluid dynamics. VIII. The

Galerkin/Least-Square method for advective-diffusive equations. Computer Methods in Applied Mechanics

Engineering, 73, 1989, pp 173-189.

2. Shakib F., Hughes T., Johan Z., A new finite elements formulation for computational fluid dynamics.X. The

compressible Euler and Navier-Stokes equations. Computer Methods in Applied Mechanics Engineering, 89,

1991, pp 141-219.

3. Neuhart, D.H., Khorrami, M.R., Choudhari, M.M., Aerodynamics of a Gulfstream G550 Nose Landing Gear

Model, AIAA Paper 2009-3152, 2009.

4. Zawodny, N.S., Liu, F., Yardibi, T., Cattafeta, L.N., Khorrami, M.R., Neuhart, D., Van de Ven, T., “A

Comparative Aeroacoustic Study of a ¼-Scale Gulfstream G550 Aircraft Nose Landing Gear Model,” AIAA

Paper 2009-3153, 2009.

5. Veer N. Vatsa, David P. Lockard, Mehdi R. Khorrami, Jan-Renee Carlson, Aeroacoustic Simulation of a Nose

Landing Gear in an Open Jet Facility using FUN3D, AIAA Paper 2010-4001, 2010.

CFD Analysis on Gulfstream G550 Nose Landing Gear

Engineering

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