FRICTION Analysis Interface Module (AIM)
FRICTION Analysis Interface Module (AIM)
Introduction

Table of Contents

FRICTION AIM Overview

FRICTION provides an estimate of laminar and turbulent skin friction and form drag suitable for use in aircraft preliminary design [1]. Taken from the FRICTION manual: "The program has its roots in a program by Ron Hendrickson at Grumman. It runs on any computer. The input requires geometric information and either the Mach and altitude combination, or the Mach and Reynolds number at which the results are desired. It uses standard flat plate skin friction formulas. The compressibility effects on skin friction are found using the Eckert Reference Temperature method for laminar flow and the van Driest II formula for turbulent flow. The basic formulas are valid from subsonic to hypersonic speeds, but the implementation makes assumptions that limit the validity to moderate supersonic speeds (about Mach 3). The key assumption is that the vehicle surface is at the adiabatic wall temperature (the user can easily modify this assumption). Form factors are used to estimate the effect of thickness on drag, and a composite formula is used to include the effect of a partial run of laminar flow."

An outline of the AIM's inputs, outputs and attributes are provided in AIM Inputs and AIM Outputs and AIM Attributes, respectively.

The accepted and expected geometric representation and analysis intentions are detailed in Geometry Representation and Analysis Intent.

Upon running preAnalysis the AIM generates a single file, "frictionInput.txt" which contains the input information and control sequence for FRICTION to execute. To populate output data the AIM expects a file, "frictionOutput.txt", to exist after running FRICTION. An example execution for FRICTION looks like (Linux and OSX executable being used - see FRICTION Modifications):

friction frictionInput.txt frictionOutput.txt

FRICTION Modifications

While FRICTION is available from, FRICTION download, the AIM assumes that a modified version of FRICTION is being used. The modified version allows for longer input and output file name lengths, as well as other I/O modifications. This modified version of FRICTION, friction_eja_mod.f, is supplied and built with the AIM. During the compilation the source code is compiled into an executable with the name friction (Linux and OSX) or friction.exe (Windows).

Examples

An example problem using the FRICTION AIM may be found at FRICTION Examples.