Direct Simulation Monte Carlo Method in Industrial Applications

In the present work three different applications of DSMC method to problems of industrial interest are revised and deepen by using both other methodologies and a more updated or advanced DSMC code, compared with those already used by other researchers to solve the same problems. For each problem, a preliminary rarefaction analysis verifies that the molecular approach, therefore the use of a DSMC code, is proper. More specifically, in this work the “sophisticated” DS2V (Ver.4.5) code has been used for the simulation of the flow fields in a deposition chamber and in a micro-channel as well as for the evaluation of viscosity of mixtures. The present work is an improvement of former works about the same topics because: 1) a method is proposed for the evaluation of the film distribution on the substrate. Furthermore, as the thin film deposition process is based on expanding thermal plasma from a torch, the influences of mass flow rate and of electrical power, supplied to the gas, and of the fluid-dynamic characteristics of the plasma jet, linked to geometry of different nozzles, are analyzed. 2) Some fluid-dynamic parameters in a micro-channel, such as load loss and impulse have been evaluated. 3) Computation of the exponent of the temperature viscosity law of a mixture of gases is proposed

Effects of SWBLI and SWSWI in Mars Atmosphere Entry

The forthcoming manned exploration missions to Mars by means of complex geometry spacecrafts stimulate the study of aerodynamic, hypersonic phenomena such as Shock Wave-Boundary Layer Interaction (SWBLI) and Shock Wave-Shock Wave Interaction (SWSWI) also along the entry in Mars atmosphere. As already done by Zuppardi and co-workers in early papers where SWBLI and SWSWI were studied in Earth re-entry, also the present study has been carried out computationally by means of a DSMC code. The aim of the present paper is to quantify the effects of SWBLI and of SWSWI at the conditions of Mars entry and to compare these effects with those, already computed by the author at the conditions of Earth re-entry. Also in this paper, SWBLI has been studied considering an external, oblique shock wave impinging onto a flat plate on which gas was flowing and therefore a boundary layer was present. Computations have been carried out in the altitude interval 55-70 km. SWSWI has been studied considering the interaction of the shock wave on the leading edge of an airfoil (NACA-0010) with the shock wave stemming from the airfoil concave, lower surface at the hinge position in flapped configuration. Computer tests have been carried out at the altitude of 65 km, in the range of angles of attack 0-40 deg and considering three flap deflections: 0, 15, 30 deg. The quantification of the effects of both interactions has been carried out by means of the relative increase of local quantities such as the resultant of pressure, normal and tangential stresses and the heat flux. SWSWI has been quantified also in terms of global aerodynamic coefficients. The analysis verified that the SWBLI effects are higher in Earth re-entry. SWSWI is also higher in Earth re-entry in terms of global coefficients but the effects are higher in Mars entry in terms of the relative increase of local quantities

Effects of chemistry in Mars entry and Earth re-entry

This paper is the follow-on of a previous paper by the author where it was pointed out that the forthcoming, manned exploration missions to Mars, by means of complex geometry spacecraft, involve the study of phenomena like shock wave-boundary layer interaction and shock wave-shock wave interaction also along the entry path in Mars atmosphere. The present paper focuses the chemical effects both in the shock layer and on the surface of a test body along the Mars orbital entry and compares these effects with those along the Earth orbital re-entry. As well known, the Mars atmosphere is almost made up of Carbon dioxide whose dissociation energy is even lower than that of Oxygen. Therefore, although the Mars entry is less energized than the Earth re-entry, one can expect that the effects of chemistry on aerodynamic quantities, both in the shock layer and on a test body surface, are different from those along the Earth re-entry. The study has been carried out computationally by means of a direct simulation Monte Carlo code, simulating the nose of an aero-space-plane and using, as free stream parameters, those along the Mars entry and Earth re-entry trajectories in the altitude interval 60-90 km. At each altitude, three chemical conditions have been considered: 1) gas non reactive and non-catalytic surface, 2) gas reactive and non-catalytic surface, 3) gas reactive and fully-catalytic surface. The results showed that the number of reactions, both in the flow and on the nose surface, is higher for Earth and, correspondingly, also the effects on the aerodynamic quantities

An evaluation of three experimental processes for two-dimensional transonic tests

The aerodynamic measurements in conventional wind tunnels usually suffer from the interference effects of the sting supporting the model and the test section walls. These effects are particularly severe in the transonic regime. Sting interference effects can be overcome through the Magnetic Suspension technique. Wall effects can be alleviated by: testing airfoils in conventional, ventilated tunnels at relatively small model to tunnel size ratios; treatment of the tunnel wall boundary layers; or by utilization of the Adaptive Wall Test Section (AWTS) concept. The operating capabilities and results from two of the foremost two-dimensional, transonic, AWTS facilities in existence are assessed. These facilities are the NASA 0.3-Meter Transonic Cryogenic Tunnel and the ONERA T-2 facility located in Toulouse, France. In addition, the results derived from the well known conventional facility, the NAE 5 ft x 5 ft Canadian wind tunnel will be assessed. CAST10/D0A2 Airfoil results will be used in all of the evaluations

DSMC Aero-Thermo-Dynamic Analysis of a Deployable Capsule for Mars Entry

A deployable capsule is made of flexible, high temperature resistant fabric, folded at launch and deployed in space at the beginning of the re-entry. This kind of capsule thanks to lightness and to low costs can be an alternative to the current “conventional“ capsules. The present authors already analyzed the trajectory and the aerodynamic behavior of such a kind of capsule during the Earth re-entry. In that study an aerodynamic longitudinal stability analysis and an evaluation of the thermal and mechanical loads for a possible, suborbital re-entry demonstrator, was carried out in both continuum and rarefied regimes. The results verified that a stable equilibrium condition is verified around the zero angle of attack and an unstable equilibrium condition is verified around the 180 angle of attack; therefore the capsule turned out to be self-stabilizing. In the present paper the trajectory, the longitudinal stability, the thermal and mechanical loads of the same capsule has been evaluated for a possible use in Mars entry. The present study is aimed at providing preliminary information considering both the diversity of the two atmospheres and the diversity of the two types of entry: ballistic, sub-orbital for Earth, direct for Mars and therefore of the initial entry velocity. The parameters were compared with those along the Earth re-entry. As the computer tests have been carried out at high altitudes, therefore in rarefied flow fields, the use of Direct Simulation Monte Carlo codes has been mandatory. The computations involved both global aerodynamic quantities (drag and longitudinal moment coefficients) and local aerodynamic quantities (heat flux, pressure and skin friction distributions along the capsule surface). The results verified that the capsule at high altitude (100 km) in Mars entry is not self-stabilizing; it is stable both around the nominal attitude or at zero angle of attack and around the reverse attitude or at 180 deg angle of attack. Furthermore, due to the much higher entry velocity, the local quantities are of several orders of magnitude higher than the ones in Earth re-entry

Aerodynamic control capability of a wing-flap in hypersonic, rarefied regime: Part II

The attitude control of an aircraft is usually fulfilled by means of thrusters at high altitudes. Therefore, the possibility of using also aerodynamic surfaces would produce the advantage of reducing the amount of fuel for the thrusters to be loaded on board. For this purpose, Zuppardi already considered some aerodynamic problems linked to the use of a wing flap in a previous paper. A NACA 0010 airfoil with a trailing edge flap of 35% of the chord, in the range of angle of attack 0-40 deg and flap deflections up to 30 deg was investigated. Computer tests were carried out in hypersonic, rarefied flow by a direct simulation Monte Carlo code at the altitudes of 65 and 85 km of Earth Atmosphere. The present work continues this subject, considering the same airfoil and free stream conditions but two flap extensions of 45% and 25% of the chord and two flap deflections of 15 and 30 deg. The main purpose is to compare the influence of the flap dimension with that of the flap deflection. The present analysis is carried out in terms of: 1) percentage variation of the global aerodynamic coefficients with respect to the no-flap configuration, 2) increment of pressure and heat flux on the airfoil lower surface due to the shock wave-shock wave interaction with respect to the same quantities in no-flap configuration, 3) flap hinge moment. Issues 2) and 3) are important for the design of the mechanical and thermal protection system and of the flap actuator. Even though the flap deflection is aerodynamically more effective than the flap extension, tests verify that using a smaller deflection angle involves the advantage of a smaller increment of pressure and heat flux on the airfoil lower surface as well as a smaller hinge moment

Aero-Thermo-Dynamic Analysis of a Low Ballistic Coefficient Deployable Capsule in Earth Re-Entry

The paper deals with a microsatellite and the related deployable recovery capsule. The aero-brake is folded at launch and deployed in space and is able to perform a de-orbiting controlled re-entry. This kind of capsule, with a flexible, high temperature resistant fabric, thanks to its lightness and modulating capability, can be an alternative to the current “conventional” recovery capsules. The present authors already analyzed the trajectory and the aerodynamic behavior of low ballistic coefficient capsules during Earth re-entry and Mars entry. In previous studies, aerodynamic longitudinal stability analysis and evaluation of thermal and aerodynamic loads for a possible suborbital re-entry demonstrator were carried out in both continuum and rarefied regimes. The present study is aimed at providing preliminary information about thermal and aerodynamic loads and longitudinal stability for a similar deployable capsule, as well as information about the electronic composition of the plasma sheet and its possible influence on radio communications at the altitudes where GPS black-out could occur. Since the computer tests were carried out at high altitudes, therefore in rarefied flow fields, use of Direct Simulation Monte Carlo codes was mandatory. The computations involved both global aerodynamic quantities (drag and longitudinal moment coefficients) and local aerodynamic quantities (heat flux and pressure distributions along the capsule surface). The results verified that the capsule at high altitude (150 km) is self-stabilizing; it is stable around the nominal attitude or at zero angle of attack and unstable around the reverse attitude or at 180 deg angle of attack. The analysis also pointed out the presence of extra statically stable equilibrium trim points

Aerodynamic Analysis of the Aerospaceplane HYPLANE in Supersonic Rarefied Flow

HyPlane is the Italian aerospaceplane proposal targeting, at the same time, both the space tourism and point-to-point intercontinental hypersonic flights. Unlike other aerospaceplane projects, relying on boosters or mother airplanes that bring the vehicle to high altitude, HyPlane will take off and land horizontally from common runways. According to the current project, HyPlane will fly sub-orbital trajectories under high-supersonic/low-hypersonic continuum flow regimes. It can go beyond the von Karman line at 100 km altitude for a short time, then starting the descending leg of the trajectory. Its aerodynamic behavior up to 70 km have already been studied and the results published in previous works. In the present paper some aspects of the aerodynamic behavior of HyPlane have been analyzed at 80, 90 and 100 km. Computer tests, calculating the aerodynamic parameters, have been carried out by a Direct Simulation Monte Carlo code. The effects of the Knudsen, Mach and Reynolds numbers have been evaluated in clean configuration. The effects of the aerodynamic surfaces on the rolling, pitching and yawing moments, and therefore on the capability to control attitude, have been analyzed at h=100 km. The aerodynamic behavior has been compared also with that of another aerospaceplane at 100 km both in clean and flapped configuration

On the Formation and Accumulation of Solid Carbon Particles in High-Enthalpy Flows Mimicking Re-Entry in the Titan Atmosphere

The problem relating to the formation of solid particles enabled by hypersonic re-entry in methane-containing atmospheres (such as that of Titan) has been tackled in the framework of a combined experimental-numerical approach implemented via a three-level analysis hierarchy. First experimental tests have been conducted using a wind tunnel driven by an industrial arc-heated facility operating with nitrogen as working gas (the SPES, i.e., the Small Planetary Entry Simulator). The formation of solid phases as a result of the complex chemical reactions established in such conditions has been detected and quantitatively measured with high accuracy. In a second stage of the study, insights into the related formation process have been obtained by using multispecies models relying on the NASA CEA code and the Direct Simulation Monte Carlo (DSMC) method. Through this approach the range of flow enthalpies in which carbonaceous deposits can be formed has been identified, obtaining good agreement with the experimental findings. Finally, the deposited substance has been analyzed by means of a set of complementary diagnostic techniques, i.e., SEM, spectroscopy (Raman, FTIR, UV-visible absorption and fluorescence), GC-MS and TGA. It has been found that carbon produced by the interaction of the simulated Titan atmosphere with a solid probe at very high temperatures can be separated into two chemically different fractions, which also include "tholins"

Solid carbon produced during the simulation of re-entry in the Titan atmosphere by means of an arc-driven flow facility

Spacecraft entry into Titan’s atmosphere has been investigated using a dedicated (Small Planetary Entry Simulator) facility (SPES). While in earlier works much attention was paid to the joint numerical-experimental simulation of typical entry physical parameters (namely, heat flux and total enthalpy); in the present analysis we focus on some unexpected results recently obtained at the University of Naples, in collaboration with CNR, in the framework of a new test campaign dedicated to various planetary atmospheres (including Titan itself). Such findings concern the presence of a carbon-like substance on the surface of the measuring probes used for the experiments, which seem to align with the results yielded by other authors with other strategies (an inductive plasma torch). We have confirmed the carbonaceous nature of such particulate matter via various diagnostic techniques such as SEM, Raman, FT-IR, UV-visible absorption and fluorescence spectroscopy, GC-MS and TGA. The present work is devoted to the presentation of such results together with a critical discussion of the novelty relating to the present experimental approach (arc plasma versus inductive torch) and an analysis of the chemical-physical differences pertaining to the carbon obtained with the two different methods