Unsteady simulation of intake ground vortex ingestion in

InVIGO - take ortex ngestion in round perations

Unsteady simulation of intake ground vortex ingestion in real wind tunnel

conditions

R. Mendonça e Costa, G. Millot, S. Raynal, (Altran) J.P. Bouchet, S. Courtine (CSTB)

12.04.2021

FP103-Aero2020-mendonca

1.Introduction

1. InVIGO and ground vortex

Project description

3 Unsteady simulation of intake ground vortex ingestion in real wind tunnel conditions – Mendonça e Costa et al. – 3AF 2020 +1

INVIGO project

Intake Vortex Ingestion in Ground Operations

▪ EU project within H2020 CleanSky2 program (Engine Integrated Technology

Demonstrator) (10/2019 → 01/2022)

▪ Two main actors :

▪ ALTRAN (Fluids and Thermal, Toulouse): Project Coordinator, CFD, Data

Analytics

▪ CSTB (Jules Verne WT, Nantes): Wind Tunnel campaigns

▪ Project supervised by EU and SAFRAN Aircraft Engines (Topic Leader)

▪ Key outcomes

▪ Methods able to predict ground vortex characteristics from reduced

instrumentation using data science approach

▪ Ground vortex measurement campaign(s) with both detailed and reduced

instrumentation

▪ CFD numerical simulations of ground vortex

Yadlin & Shmilovich, 2006

1. Introduction

4

Vortex formation

Wind direction

Wind velocity

Engine vibrations; suction of abrasive particles

Inlet air speed

Unsteady simulation of intake ground vortex ingestion in real wind tunnel conditions – Mendonça e Costa et al. – 3AF 2020 +1

2.Computational Domain and generated grids

2. Computational domain and generated grids

6

Reference geometry: Jules Verne Climatic Wind Tunnel (WT), CSTB, Nantes


1/6.5 scale nacelle with test mock-up

Vertically moving table for nacelle

ground clearance adjustment

Glass area for Stereo-PIV acquisition

CSTB Jules Verne WT

2. Computational domain and generated grids

7

WT configuration Isolated configuration

WT configuration (top); isolated

configuration (bottom)

Setup Grid size (elements)

Isolated configuration 47 M

WT configuration 57 MMax. Cell size [m]

BOI nacelle lips 𝟐. 𝟒𝟏 × 𝟏𝟎−𝟑

BOI inlet 𝟒. 𝟖𝟑 × 𝟏𝟎−𝟑

BOI ground region vortex

vicinity

𝟔. 𝟒𝟒 × 𝟏𝟎−𝟑


3.Problem formulation and numerical setup

3. Problem formulation

9

Steady simulations

RANS + 𝑘𝜔 − 𝑆𝑆𝑇 for closure

Unsteady simulations

SAS (Scale Adaptive Simulations)1

Verification of characteristic time and length scales:

• Vortex length (Kolmogorov) scales > grid size in vortex vicinity

→ grid resolution OK

• Range of time scales of interest determined

→ appropriate timestep selection for unsteady calculation


• Need for characterizing ground vortex on many ground clearance, wind speed, intake velocity combinations.

• Numerical simulations showed that steady simulations were not efficient for some challenging cases.

• Steady and Unsteady simulations have to be considered.

1F.R. Menter, Y. Egorov: The Scale−Adaptive Simulation Method

for Unsteady Turbulent Flow Predictions. Part 1:

Theory and Model Description (2010)

3. Numerical setup: boundary conditions

10

WT configuration Isolated configuration

Velocity-inlet

condition: 90° wind

velocity, 10 m/s

crosswind

Pressure-outlet

condition: ambient, non

disturbed conditions

Pressure-outlet condition: target Mass Flow rate (10 kg/s),

followed by pressure specificationUnsteady simulation of intake ground vortex ingestion in real wind tunnel conditions – Mendonça e Costa et al. – 3AF 2020 +1

Height to inlet

diameter ratio (H/D):

0.85

U*=𝑼𝒊/𝑼𝒘𝒊𝒏𝒅: 8.5

3. Numerical setup: convergence verification

11

WT configuration

Isolated configuration

Both configurations (WT and

isolated) tested at identical

intake mass flow rate

(difference within 1%)


Total pressure distribution (relative to undisturbed pressure) on the reference fan

plane for the WT (top) and isolated (bottom) configuration. Solution at flow time of

0.79s.

4.Results

4.1 Results: comparison between isolated and WT configurations

13

WT

co

nfi

gu

rati

on

Iso

late

dc

on

figu

ratio

n


Both configurations (WT and

isolated) display similar path

lines, namely in vortex

vicinity

Vortex related

phenomena can be

safely analysed in a

simplified/isolated

configuration: little to

no influence from

experimental setup for

this operating point

Path lines (coloured by velocity magnitude) entering the reference fan plane. Solution at flow time of 0.79s

4.2 Post-processing strategies: distortion index to locate vortex

centre

14

How to determine:

• 1), 2) vortex centre (radial and azimuthal

coordinates)

• 3), 4) vortex radius and 𝑉𝜃

1, 2

3, 4

Vortex centre

determination

based on

distortion

indexes

𝑫𝑪𝜽 =𝑷𝒇 − 𝑷𝜽

𝒒𝒇

𝑰𝑫𝑪 = 𝐦𝐚𝐱𝒓∈[𝟎;𝒓𝒎𝒂𝒙]

𝑷𝒕,𝒓 − 𝑷𝒕,𝒓𝒎𝒊𝒏

𝑷𝒕

Vortex centre

coordinates determined

at the end of the steady

simulation

How to ensure vortex tracking

throughout the unsteady simulation?


4.3 Vortex tracking: Q-criterion iso-clips

15

• Define a circular region centred on the pre-determined vortex centre,

quasi-tangent to the extremity of the reference fan plane.

• Set 10 Q-criterion iso-clips on the defined circular region, with different

minimum and maximum threshold:

Q-criterion iso-clip

minimum threshold [s-1]

Q-criterion iso-clip

maximum threshold [s-1]

1 × 103 6 × 1012

1 × 104 6 × 1012

1 × 105 6 × 1012

2 × 105 6 × 1012

5 × 105 6 × 1012

1 × 106 6 × 1012

2 × 106 6 × 1012

5 × 106 6 × 1012

1 × 107 6 × 1012

2 × 107 6 × 1012

captures the entire vortex

and its immediate vicinity

captures the vortex core

Iso-clip

decreasing

in areaReference fan plane Q-criterion distributions taken

at equal intervals up to 0.1965s of flow time.

Circular region enclosing the vortex highlighted in

white.


4.4 Vortex monitoring: Q-criterion iso-clips

16

On the 10 Q-criterion iso-clips 𝒄 = 𝒄𝟏, 𝒄𝟐, … , 𝒄𝟏𝟎 monitor the following

variables throughout the unsteady simulation:

• Area of each clip;

• Circulation Γ on each clip (computed as the surface integral of the

vorticity component perpendicular to each reference plane

• Area-weighted average coordinates of each one of the iso-clips

𝑟𝑒𝑞 𝑐, 𝑡 =𝐴𝑐𝑙𝑖𝑝𝜋

𝑉𝜃(𝑐, 𝑡) =Γ

2𝜋𝑟𝑒𝑞(𝑐, 𝑡)

𝑟𝑣𝑜𝑟𝑡𝑒𝑥 𝑐𝑒𝑛𝑡𝑟𝑒 = 𝑓 𝑐, 𝑡𝜃𝑣𝑜𝑟𝑡𝑒𝑥 𝑐𝑒𝑛𝑡𝑟𝑒 = 𝑓(𝑐, 𝑡)



17

For a given instant in time, 𝒕 = 𝒕𝟏, equivalent vortex radius 𝑟𝑒𝑞 and 𝑉𝜃 can be determined

using the information from all the retrieved iso-clips 𝒄 = 𝒄𝟏, 𝒄𝟐, … , 𝒄𝟏𝟎 :

The maximum of the curve 𝑽𝜽 = 𝒇(𝒓𝒆𝒒) yields the vortex radius

and 𝑉𝜃 corresponding to a given instant 𝑡 = 𝑡1.

The average coordinates of the smallest iso-clip (capturing

vortex core only) will yield an accurate estimation of

𝒓𝒗𝒐𝒓𝒕𝒆𝒙 𝒄𝒆𝒏𝒕𝒓𝒆 = 𝒇 𝒕 and 𝜽𝒗𝒐𝒓𝒕𝒆𝒙 𝒄𝒆𝒏𝒕𝒓𝒆 = 𝒇(𝒕)

Performing this exercise for all instants 𝑡 of the simulation, one can obtain 𝒓𝒆𝒒 = f(t) and 𝑽𝜽 = f(t)



18

The variables of interest appear

to be in fair agreement for both

studied setups (isolated nacelle

and WT configuration).

Significant oscillations observed

in the evolution of variables over

time, for both configurations:

deeper analysis of the devised

tracking methodology.

Can the biggest Q-

criterion iso-clips

(lower threshold)

capture additional

structures in vortex

vicinity?


Q-criterion distribution (log scale) on the reference fan plane;

representation of lowest threshold Q-criterion iso-clip.

5.Conclusion and future work

5. Conclusion and future work

20

• Comparison between the unsteady

simulation of ground vortex formation and

ingestion in two different configurations:

isolated nacelle vs. WT;

• No major differences in terms of vortex

phenomena between both setups → little to

no influence from the geometry/elements in

the experimental facility, for this operating

point;

• Automated determination of vortex centre

for a given steady solution;

• Tracking of vortex centre coordinates,

vortex radius and 𝑉𝜃 over the course of an

unsteady simulation.

Milestones achieved Future work

• Improvement of the tracking strategy for

unsteady simulations: detection of Q-

criterion iso-contours from the vortex centre

and moving outwards → compute

circulation Γ along each contour;

• Retrieve data from reference planes (fan,

PIV) periodically for a posteriori analysis;

• Construction and assimilation

of an experimental database

of velocity fields and pressure

measurements scanning a

wide range of H/D and U *

parameters


5 m/s

10 m/s

15 m/s

20 m/s

Adapted from M. Jermy and W.H. Ho: Location of the vortex

formation threshold at suction inlets near ground planes by computational fluid

dynamics simulation (2008)

Acknowledgements : European Union, Safran Aircraft EnginesThe InVIGO project has received funding from the Clean Sky 2 Joint Undertaking under the European

Union’s Horizon 2020 research and innovation programme under grant agreement No 864288

This communication and the data provided here represent only the authors’ view and do not engage Clean

Sky 2 nor the European Union for any use that may be made of the information they contain.

Thank you for your attention

Contacts : [email protected], [email protected],

[email protected], [email protected], [email protected]

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Unsteady simulation of intake ground vortex ingestion in