Modeling of sanal flow choking condition and design optimization of high performance dual-thrust SRMs

Sanal Kumar, VR and Sankar, V and Chandrasekaran, N and Sulthan Ariff Rahman, M (2018) Modeling of sanal flow choking condition and design optimization of high performance dual-thrust SRMs. In: 54th AIAA/SAE/ASEE Joint Propulsion Conference, 2018, 9 - 11 July 2018, Cincinnati, Ohio.

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Abstract

A powerful closed-form analytical model is developed for predicting the 3D boundary layer displacement thickness at the Sanal flow choking condition for diabatic flows for the validation, verification and calibration of various viscous flow solvers. This is the continuation of our previous connected paper pertaining to the boundary layer blockage prediction for adiabatic flows at the choked flow condition (V. R. Sanal Kumar et al. 1, AIP Advances, 8, 025315, 2018). The Sanal flow choking for diabatic flow is a unique condition of any internal flow system at which both the thermal choking (Rayleigh flow effect) and the wall-friction induced flow choking (Fanno flow effect) occur at a single sonic-fluid-throat location. A constant area circular duct with large length-to-diameter ratio (l/d > 27) followed by a divergent cylindrical port is selected as a three-dimensional physical model. A well-posed initial condition is prescribed for this model for capturing the physics of compressible diabatic viscous flows at the choked flow condition. During the numerical simulation, for achieving the Sanal flow choking effect the inlet Mach number is selected based on the thermal choking condition of the ideal gas and the average wall friction coefficient of the cylindrical port is selected based on the Fanno flow model. The beauty and novelty of the Sanal flow choking model is that without missing the real flow physics we could exactly predict the 3D boundary layer blockage of the dual-thrust solid rocket motors (SRMs) at the sonic fluid-throat from the known values of the inlet port diameter, inlet Mach number, and the heat capacity ratio of the gas. We found from the exact solutions that at the identical inflow conditions the analytically predicted 3D boundary layer blockage at the sonic-fluid-throat is 45.12 % lower than the 2D boundary layer blockage of a cylindrical port system with air as the working fluid obeying the compressible diabatic viscous flows theory. The results presented herein corroborated that any fluid flow solver, with an appropriate turbulence model, a best fit law of viscosity and wall-friction, calibrated using the proposed closed-form analytical model at the Sanal flow choking condition with state-of-the-art is considered as credible for the grain design optimization of dual-thrust SRMs with the highest promising propellant loading density within the given envelope without manifestation of any internal flow choking leading to possible shock waves causing catastrophic failures. Furthermore, the exact prediction of the 3D boundary layer displacement thickness at the sonic-fluid-throat of any internal system at the Sanal flow choking condition provides a means to correctly pinpoint the causes of errors of the viscous flow solvers.

Item Type:	Conference Paper
Publication:	2018 Joint Propulsion Conference
Publisher:	American Institute of Aeronautics and Astronautics Inc, AIAA
Additional Information:	The copyright for this article belongs to the American Institute of Aeronautics and Astronautics, Inc.
Keywords:	Aerodynamics; Air; Analytical models; Boundary layers; Flow simulation; Forecasting; Friction; Mach number; Propulsion; Shock waves; Specific heat; Turbulence models; Viscous flow, Catastrophic failures; Choked-flow condition; Design optimization; Displacement thickness; Initial conditions; Length to diameter ratio; Solid rocket motors; Verification and calibrations, Boundary layer flow
Department/Centre:	Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Date Deposited:	14 Aug 2022 06:16
Last Modified:	14 Aug 2022 06:16
URI:	https://eprints.iisc.ac.in/id/eprint/75750

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