S-duct Test case detail

The overall goal of the Propulsion Aerodynamics Workshop (PAW) is to assess accuracy of existing computer codes and modeling techniques in simulating flows of interest to the propulsion community.  To achieve this goal, the AIAA has supported and continues to support the Air Breathing Propulsion System Integration (ABPSI) sub-committee in sponsoring Propulsion Aero Workshops where results of existing CFD codes can be compared with measured data for benchmark inlet and nozzle flow cases.  This document presents the inlet test cases to be studied in the Third Propulsion Aerodynamics Workshop (PAW03) to be held at the 52nd Joint Propulsion Conference in Salt Lake City, Utah, USA, from July 25-27, 2016.

The specific goals of Inlet PAW03 are derived from feedback from the previous two PAWs.  At the end of PAW02, several areas of further investigation were suggested and included:


From existing solutions/submittals:

1.      Calculate and compare turbulence quantities (TKE, eddy viscosity, etc.)

2.      Calculate and compare swirl (Use AIR5686 for swirl descriptor definition)

3.      Examine RMS of differences between experiment and CFD probe total pressures

4.      Calculate and compare other SAE 1420B distortion descriptors (i.e extent, MPR, etc)

New work:

1.      Conduct time-accurate CFD studies

2.      Have participants examine the following on currently available data base and existing grids (S-duct with and without VGs)

(a)   Far field boundary conditions (i. e. M=0.1, 0.05, 0.002, 0.001, 0.0001, etc)

(b)   Downstream boundary condition (mass flow, constant pressure, others)

(c)   y+ (10, 1, 0.5, 0.1, 0.05, etc)

(d)   Use of wall functions

(e)   AIP probe modeling effect

Participants are certainly welcome to select any one of these topics for further investigation.  However, there are currently two areas of prime interest to the Inlet sub-committee of the PAW as well as a third one derived from the work of PAW02.  First, considerable work has been done on an S-Duct using steady-state RANS which could be used to address any one of the first 4 topics listed above.  However, while inlet designers are interested in steady-state AIP properties such as recovery and distortion, it is really the time-dependent flow character that affects inlet/engine operability.  Consequently, the Inlet PAW committee is interested in examining results from time-accurate solutions of the flow field.  In order to compare results with experimental data, it is of course necessary to have dynamic data available.  While such data exists for the S-Duct from PAW01 and PAW02, it is not readily available.  However, there is a set of both steady-state and dynamic data available from an S-Duct that is in the public domain.  This geometry and data is proposed for use in PAW03.  The geometry is described in Section 3 of this document and the selected flow conditions are listed in Section 4.

A second area of interest to the PAW is the affect that the presence of pressure instrumentation has on computed results.  Again, detailed geometric data is available for the AIP instrumentation used in the aforementioned test.  This instrumentation is also described and presented in Section 3.

A third area of interest is the effect of flow control devices on inlet flow fields.  Both geometry as well as steady-state and dynamic data are available from the same test for a configuration with large vortex generators.  This geometry is also presented in Section 3 with flow conditions shown in Section 4.


General Guidelines

Participants are encouraged to address any of the main topics listed above.  The degree of success of the CFD methods will be judged against measured data such as steady-state inlet recovery and distortion, and flow field surveys of static and total pressure in regions of interest.  However, the Inlet committee is keenly interested in the three areas mentioned above:

1.      Comparisons of AIP flow properties resulting from time-accurate computations.

2.      Effect the presence of AIP pressure instrumentation has on steady-state and/or dynamic total pressure and distortion at the AIP.

3.      Effect of flow control devices on AIP flow properties, steady-state and/or dynamic.

The time-accurate computations can be made without the AIP rake/probe instrumentation present; this will simplify the amount of computational effort required.  It is recommended that results aimed at determining the effect of AIP instrumentation should be done using steady-state computations (i. e. RANS) though time-accurate results would be welcomed.  Finally, the effect of flow control devices (i. e. vortex generators) can be done using either steady-state or time-accurate methods.  The Inlet committee requests that participants inform the committee what area(s) the participant is addressing.

In order to disseminate information in a timely manner and allow participants adequate time to compute results, only the basic information is provided in this document.  The geometry and flow conditions are defined.  The details of pressure instrumentation, comparison plots, past-processing expectations, etc. will be provided in a later revision of this document.


For PAW03 a new S-Duct geometry is provided from a NASA contract that investigated the effects of boundary-layer ingestion (BLI) and flow control techniques on inlet system performance.  The work is summarized in NASA CR-2011-217237 (http://ntrs.nasa.gov/search.jsp?R=20120002597).  

IFCPT Basic Duct Geometry

The model is composed of a large bell mouth contraction, a front adapter section, an S-shaped BLI duct, an AIP housing, another adapter section, and a diffuser.  Tests were conducted at Georgia Tech’s Transonic Tunnel shown in Figure 1.   Air was induced from ambient room conditions through the diffuser by creating a low pressure at the downstream end with a vacuum pump.  Airflow was controlled by running the pump at selected RPMs and airflow was measured with a calibrated Mass Flow Plug (MFP). These basic elements are highlighted in Figure 2.  The main elements to be modeled for this test case are the bell mouth contraction, front adapter section, IFCPT S-duct, AIP housing, and extension.  These elements are depicted in Figure 3.  The IFCPT S-Duct has an AIP diameter, D, of 5 inches, is offset 1.09D in the vertical direction, and has an L/D of 3.106 (L=15.52894 inches) not including a ½ D constant straight area section ahead of the duct throat.  The model provided has a 5D extension added in order to impose the downstream constant pressure or mass flow boundary condition.

Paw Aiaa,
Feb 17, 2016, 8:57 AM
Paw Aiaa,
Jun 29, 2016, 7:43 AM
Paw Aiaa,
Jun 29, 2016, 7:43 AM