Gennaro Zuppardi

Aero-thermo-dynamic analysis of the Spaceliner-7.1 vehicle in high altitude flight

SpaceLiner, designed by DLR, is a visionary, extremely fast passenger transportation concept. It consists of two stages: a winged booster, a vehicle. After separation of the two stages, the booster makes a controlled re-entry and returns to the launch site. According to the current project, version 7-1 of SpaceLiner (SpaceLiner-7.1), the vehicle should be brought at an altitude of 75 km and then released, undertaking the descent path. In the perspective that the vehicle of SpaceLiner-7.1 could be brought to altitudes higher than 75 km, e.g. 100 km or above and also for a speculative purpose, in this paper the aerodynamic parameters of the SpaceLiner-7.1 vehicle are calculated in the whole transition regime, from continuum low density to free molecular flows. Computer simulations have been carried out by three codes: two DSMC codes, DS3V in the altitude interval 100-250 km for the evaluation of the global aerodynamic coefficients and DS2V at the altitude of 60 km for the evaluation of the heat flux and pre...

Analysis of Bridging Formulae in Transitional Regime

The most suitable method to compute aerodynamic forces of a spacecraft, at first stage of a design, relies on bridging formulae. There are two kinds of bridging formulae: global and local. The global formulae rely on knowledge of spacecraft aerodynamic force coefficients in continuum and in free molecular flow. The local formulae calculate the skin friction and pressure coefficients on the body surface; the global aerodynamic coefficients are then computed by integration. The aim of this work is to analyze the widely accepted local formulae by Potter and by Kotov. To this purpose, a simple body, like a sphere, has been preliminary considered and the results have been compared with those from the DSMC code DS2V. This comparison led to the corrections of the computation of the skin friction and pressure coefficients. These corrections have been applied to the Potter formula. On the other hand the original Kotov formula showed good results for the pressure coefficient at high altitudes. Therefore a merge of ...

Teaching aerodynamics using a microcomputer

Abstract An interactive and wholly automatized computer code has been developed on a microcomputer for the aerodynamic analysis of airfoils in incompressible now fields. It is intended to serve as a useful support in teaching aerodynamics. The code contains a number of modules (or blocks) for: (1) drawing the shape with the help of an interactive graphic device interfaced with the microcomputer; (2) computing the aerodynamic inviscid and viscous flow field and the aerodynamic coefficients; (3) modifying and/or correcting the body shape and then computing the new aerodynamic coefficients. In this way the student can evaluate, operating directly and interactively, the influence of the changes in shape on the aerodynamics of the airfoil under study.

Influence of chemical models on heat flux for EXPERT and Orion capsules

The computation of heat flux on two current re-entry capsules, European eXPErimental Reentry Testbed (EXPERT) and Orion, has been carried out by a direct simulation Monte Carlo code (DS2V) and by a computational fluid dynamic code (H3NS) in transitional regime, considering both non-reactive and fully catalytic surface. These capsules have been chosen for this analysis because they have been characterized by completely different shapes and re-entry trajectories. DS2V and H3NS use the Gupta and the Park chemical models, respectively. The results showed that the heat flux predicted by DS2V is always higher than that predicted by H3NS. Therefore, a sensitivity analysis of the chemical models on the heat flux has been carried out for both capsules. More specifically, the Park model has been implemented in DS2V as well. The results showed that DS2V and H3NS compute a different chemical composition both in the flow field and on the surface, even when using the same chemical model (Park); therefore, the different results obtained from the two codes can be attributed mostly to the different methodology used in handling all chemical processes.

Analysis of Aero‐Thermodynamic Behavior of EXPERT Capsule in Transitional Regime

The aerodynamic behavior of the EXPERT capsule has been already widely studied at low altitudes. In order to broaden the aerodynamic data base of the capsule, additional computations of the aerodynamic forces and an evaluation of the longitudinal stability and fluctuation of the pressure center have been carried out in the altitude interval 80–105 km. The effect of the rolling angle has been also evaluated. As EXPERT, in the considered altitude interval is in transitional regime, computations have been made by the DSMC code DS3V. Heat flux along the capsule surface has been also evaluated. This is an important topic because the nose and the frustum are made of low and high catalyticity materials, respectively. Computations, already performed in continuum regime by the CFD code H3NS, showed that, at the nose‐frustum junction, an abrupt and strong peak of heat flux is present. In this work, this problem has been analyzed also in transitional regime. For this application, the DSMC 2‐D code DS2V, requiring sm...

Aerodynamic characterization of the jet of an arc wind tunnel

It is well known that, due to a very aggressive environment and to a rather high rarefaction level of the arc wind tunnel jet, the measurement of fluid-dynamic parameters is difficult. For this reason, the aerodynamic characterization of the jet relies also on computer codes, simulating the operation of the tunnel. The present authors already used successfully such a kind of computing procedure for the tests in the arc wind tunnel (SPES) in Naples (Italy). In the present work an improved procedure is proposed. Like the former procedure also the present procedure relies on two codes working in tandem: 1) one-dimensional code simulating the inviscid and thermally not-conducting flow field in the torch, in the mix-chamber and in the nozzle up to the position, along the nozzle axis, of the continuum breakdown, 2) Direct Simulation Monte Carlo (DSMC) code simulating the flow field in the remaining part of the nozzle. In the present procedure, the DSMC simulation includes the simulation both in the nozzle and i...

Influence of ionization on the Gupta and on the Park chemical models

This study is an extension of former works by the present authors, in which the influence of the chemical models by Gupta and by Park was evaluated on thermo-fluid-dynamic parameters in the flow field, including transport coefficients, related characteristic numbers and heat flux on two current capsules (EXPERT and Orion) during the high altitude re-entry path. The results verified that the models, even computing different air compositions in the flow field, compute only slight different compositions on the capsule surface, therefore the difference in the heat flux is not very relevant. In the above mentioned studies, ionization was neglected because the velocities of the capsules (about 5000 m/s for EXPERT and about 7600 m/s for Orion) were not high enough to activate meaningful ionization. The aim of the present work is to evaluate the incidence of ionization, linked to the chemical models by Gupta and by Park, on both heat flux and thermo fluid-dynamic parameters. The present computer tests were carrie...

Sensitivity analysis of the Gupta and Park chemical models on the heat flux by DSMC and CFD codes

The present study is the logical continuation of a former paper by the first author in which the influence of the chemical models by Gupta and by Park on the computation of heat flux on the Orion and EXPERT capsules was evaluated. Tests were carried out by the direct simulation Monte Carlo code DS2V and by the computational fluiddynamic (CFD) code H3NS. DS2V implements the Gupta model, while H3NS implements the Park model. In order to compare the effects of the chemical models, the Park model was implemented also in DS2V. The results showed that DS2V and H3NS compute a different composition both in the flow field and on the surface, even using the same chemical model (Park). Furthermore DS2V computes, by the two chemical models, different compositions in the flow field but the same composition on the surface, therefore the same heat flux. In the present study, in order to evaluate the influence of these chemical models also in a CFD code, the Gupta and the Park models have been implemented in FLUENT. Test...

DSMC aero-thermo-dynamic analysis of a sample-return capsule

A rarefied aero-thermo-dynamic analysis of a sample Earth Return Capsule during the high energy, high altitude re-entry path from an exploration mission is presented. The altitude interval 70-120 km is considered, where the capsule experiences different flow fields. In fact, the flow regime ranges from continuum low density to near free molecular flow and, even though the free stream velocity is almost constant (13 km/s) in the whole altitude interval, the Mach number changes from 44 to 32 and the Reynolds number, based on the capsule diameter, ranges from 4.92×104 to 9. The computations have been carried out using two direct simulation Monte Carlo codes: DS2V to compute local quantities such as heat flux, thermal and aerodynamic loads at zero angle of attack and DS3V to compute global aerodynamic coefficients in the range of the angle of attack 0-60 deg The results verified that in this altitude interval the heat flux and the thermal load reasonably satisfy specific requirements for the thermal protecti...

Comparing the Chemical Models by Fan‐Shen and by Bird through a 2D DSMC Code

The present work is the logical continuation of a paper by Zuppardi and Romano where the models by Bird and by Fan and Shen, evaluating the occurrence of a chemical reaction in a collision between two molecules, were compared in a Direct Simulation Monte Carlo (DSMC) process. The main difference between the models is in handling molecular vibration; the Bird model considers the vibrational energy only as a contribution to the collision energy, the Fan‐Shen model considers a physical link between vibrational excitation and dissociation/exchange reactions. In order to make comparable the two models, a parameter similar to the steric factor by Bird, was introduced into the DSMC implementation of the Fan‐Shen model. A “simple” DSMC code, computing just the occurrence of a reaction in the collision between two molecules, was written for that purpose. Computer tests considered three dissociation and two exchange reactions in air. The results verified that the direct influence of vibration increases the reactivi...