is introduced with the aim of simulating jet mixing under supercritical pressure environments. The nonlinear localized artificial diffusivity provides the stability to capture different types of discontinuity, such as shock wave, contact surface, and material interface, whereas the high-order compact difference scheme resolves broadband scales in the rest of the domain. The present method is tested on several one-dimensional discontinuity-related problems under super/transcritical conditions and a comparatively more illustrative two-dimensional lowtemperature planar jet problem under a supercritical pressure condition. The localized artificial diffusivity, especially artificial thermal conductivity for temperature gradients, effectively suppresses numerical wiggles near the interfaces. The effects of the artificial thermal conductivity on numerical stability and accuracy are examined. Comparisons between the present method and a conventional low-order scheme demonstrate the superior performance of the present method for resolving a wide range of flow scales while successfully capturing large density/temperature variations at interfaces.

High-Resolution Numerical Method for Supercritical Flows with Large Density Variations

CFD investigation of thermal and pressurization performance in LH2 tank during discharge

Transient thermal and pressurization performance of LO2 tank during helium pressurization combined with outside aerodynamic heating

Study on thermal stratification in liquid hydrogen tank under different gravity levels

Contrast between Steady and Time-Averaged Unsteady Combustion Simulations

Simulations of an uni-element, shear coaxial injector configuration with liquid nitrogen in the inner tube mixing with a co-flowing warm nitrogen gas stream are presented; the chamber has a supercritical pressure of 4.95 MPa with the liquid nitrogen jet temperature mildly supercritical at 129 K. Unsteady solutions on a complete three-dimensional configuration were computed using a hybrid RANS/LES framework and compared with experimental data. Our results reveal a highly unsteady flow field with strong fluctuations in the post region between the inner jet and co-flowing outer jet. This unsteadiness is caused by strong thermodynamics gradients near the critical point, which cause the inner jet to expand out radially as it mixes with the warmer fluid from the outer jet. Analysis of the turbulence field indicates that nominal temperature fluctuations generate large amplitude density fluctuations which in turn increases the Reynolds stress in the liquid jet shear layer. A key finding of this study is that the unsteady mixing is dominated by three-dimensional helical instabilities on the interface of the liquid jet shear layer. In this important respect, a trans-critical/supercritical jet is very different from a gas jet where the jet nearfield is unstable only to axisymmetric instabilities. A comparison of the mean radial temperature distribution indicates reasonable comparison with experimental measurement; the dramatic mixing of the liquid shear layer is captured well but the mixing in the outer gas shear layer is underpredicted. A comparison of the jet mixing core length prediction along the centerline with the dark core length measurements from flow visualization indicates that the numerical results overpredict the mixing and this may be due to a combination of uncertainty in the temperature measurement values as well as numerical errors.

Three-Dimensional Hybrid RANS/LES Simulations of a Supercritical Liquid Nitrogen Jet

A) Advanced Gas/Liquid Framework with Real Fluids Property Routines: I. A multi-fluid formulation in the preconditioned CRUNCH CFD(Registered TradeMark) code developed where a mixture of liquid and gases can be specified: a) Various options for Equation of state specification available (from simplified ideal fluid mixtures, to real fluid EOS such as SRK or BWR models). b) Vaporization of liquids driven by pressure value relative to vapor pressure and combustion of vapors allowed. c) Extensive validation has been undertaken. II. Currently working on developing primary break-up models and surface tension effects for more rigorous phase-change modeling and interfacial dynamics B) Framework Applied to Run-time Tanks at Ground Test Facilities C) Framework Used For J-2 Upper Stage Tank Modeling: 1) NASA MSFC tank pressurization: a) Hydrogen and oxygen tank pre-press, repress and draining being modeled at NASA MSFC. 2) NASA AMES tank safety effort a) liquid hydrogen and oxygen are separated by a baffle in the J-2 tank. We are modeling pressure rise and possible combustion if a hole develops in the baffle and liquid hydrogen leaks into the oxygen tank. Tank pressure rise rates simulated and risk of combustion evaluated.

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Computational Analyses of Pressurization in Cryogenic Tanks

Summary The pressure of propellant and oxidizer tanks has to be maintained within a narrow margin and is critical to the proper functioning of the liquid propulsion system. Several control mechanisms such as venting and spray bars are specifically deployed in the tankage to ensure that the pressure in the tank is restricted to the design margins. In this paper a suite of predictive tools have been developed that can aid in the design and management of propellant tanks. The analysis tools comprise of a multi-node lumped parameter code, a multi-phase CFD code, and a hybrid procedure that utilizes CFD in conjunction with a lumped parameter based internal boundary between the ullage and the liquid. Each tool is specifically tailored towards a certain class of tank pressurization problems: for example the multi-node lumped parameter approach is particularly suited for long duration space tank applications, while the CFD approach is applicable to short duration injection based pressurization problems where mixing is the dominant physical mechanism. In long duration cases, where injection or venting based control systems can significantly alter the flow in the tank the hybrid approach is more appealing. A series of test cases from different regimes of tank pressurization were considered in this paper with the three approaches. The first simulation was based on the Saturn AS-203 self-pressurization fuel tank experiment in a low gravity environment. The complete duration of the test was analyzed with the multi-node lumped parameter code with average heat loads through the tank walls and the

Chun P. Lee

Papers

Three-Dimensional Hybrid RANS/LES Simulations of a Supercritical Liquid Nitrogen Jet

Computational Analyses of Pressurization in Cryogenic Tanks

Progress in Modeling Pressurization in Propellant Tanks