Blunt Cone Research Articles

Analysis of electromagnetic wave propagation and scattering characteristics of plasma shealth via high order ADE-ADI FDTD

In order to avoid complicated transformations and convolutions compared with Z-transform ADI-FDTD and the PLJERC-ADI-FDTD method, the high order ADE-ADI FDTD method for unmagnetized plasma is proposed. The fourth-order spatial central difference approximation technique is used in the proposed method to reduce the numerical dispersion of the ADI scheme. The iteration method for solving equation set improves the computational efficiency. The proposed method can be easily extended to analyze other media through changing the coefficients of the auxiliary difference equation of polarization current. The validity of the proposed method is tested by calculating the reflection and transmission coefficients of a plasma slab. The simulation results show that the computational accuracy and efficiency of the proposed method are higher than those of the PLJERC-ADI-FDTD method. The plasma sheath around a hypersonic blunted cone is established by CFD-FANSTRAN, and the reflection, transmission, and attenuation coefficients of the modeled plasma sheath against frequency under different Mach numbers and heights are calculated through the proposed method. The backward RCS of the plasma sheath is also calculated through the proposed method. The electromagnetic wave propagation and scattering characteristics of the plasma sheath are analyzed via the calculation.

Influence of Thermal Protection Material Composition on Heat and Mass Exchange of Body in Spatial Supersonic Flow

The conjugate problem of aerodynamic heating of a blunted cone moving in the atmosphere at angle of attack at supersonic speed is considered. Three modifications of a thermal protection material based on coal-plastic with different proportions of a phenol-formalhyde binder and a carbon cloth are investigated. The effect of the material composition on the surface temperature and the mass loss characteristics is analyzed.

Real-Gas and Surface-Ablation Effects on Hypersonic Boundary-Layer Instability over a Blunt Cone

There has been little research into surface-ablation effects on hypersonic boundary-layer instability, and the current understanding of real-gas effects on hypersonic boundary-layer instability still contains uncertainties. The objective of the current work was to analyze the hypersonic boundary-layer transition process using linear-stability theory, in which surface ablation, as well as real-gas effects, is present, and the second mode is the dominant instability mode. A thermochemical nonequilibrium linear-stability-theory code with a gas-phase model that includes multiple carbon species, as well as a linearized surface graphite-pseudoablation model, is developed and validated. It is validated with previously published linear-stability analysis and direct-numerical-simulation results. A high-order method for discretizing the linear-stability equations is used, which can easily include high-order boundary conditions. The developed linear-stability code, with mean-flow solutions produced from a high-order shock-fitting direct-numerical-simulation method for hypersonic flows with thermochemical nonequilibrium and surface-chemistry boundary conditions for graphite pseudoablation, is used to study hypersonic boundary-layer instability for a 7 deg half-angle blunt cone at Mach 15.99 and the Reentry-F experiment at 100 kft. Multiple mean-flow simulations are obtained with the same geometry and freestream conditions to help separate real-gas, blowing, and carbon-species effects on hypersonic boundary-layer instability. For the case at Mach 15.99, an factor comparison shows that real-gas effects significantly destabilize the flow when compared to an ideal gas. Blowing is destabilizing for the real-gas simulation, and has a negligible effect for the ideal-gas simulation due to the different locations of instability onset. Notably, carbon species resulting from ablation are shown to slightly stabilize the flow for both cases. It is also found that ablating nose-cone effects may safely be excluded when determining the factor at transition for Reentry-F at 100 kft.

Effect of electric field on the morphology and mechanical properties of electrospun fibers

Three kinds of spinnerets containing single needle, sharp and blunt cones were used to study the effect of electric field distribution on the morphology and mechanical properties of the as-prepared fibers.

Design of Artificial Neuro-fuzzy Based Methodology for Six Component Force Balance

A blunt cone model of 600 apex angle and 150 flare with internally mountable accelerometer balance has been considered for the present investigation on six component force balance. The finite element method (FEM) has been incorporated at predetermined angles of the applied force to obtain multiple accelerations in three spatial directions so as to replicate a six component force balance system. A novel intelligent soft computing technique, Artificial Neuro-Fuzzy Inference System (ANFIS) has been implemented for accurate prediction of the magnitude and trend of aerodynamic forces and moments from the transient acceleration history. The same method is also used to validate the universal approximation nature of the impulse force by accurate prediction of the hat and ramp forces from the training of the impulse forces. Furthermore, a training algorithm is deduced so as to predict the force and moment magnitude for the three and single component force balance from the six component training data. Henceforth, novelty of this study involves in deduction of a universal training method and successful implementation of it to predict short duration transient force and moment histories.

Численное моделирование МГД управления сверхзвуковым потоком в среде OpenFOAM

MHD flow control is a relevant topic in today’s aerospace engineering. An OpenFOAM density-based solver that is capable of handling MHD supersonic flow problems with constant magnetic field is developed. The proposed solver is based on Balbas-Tadmor central difference schemes. This solver can be applied to studying the potential of MHD flow control systems for atmospheric entry vehicles. A supersonic flow around a spherically blunt cone both with and without MHD interaction is studied. Gases with thermodynamic parameters characteristic for Earth’s and Martian atmospheres are considered. The results show visible effect of magnetic field on surface temperature of the body. The differences between shock standoff distances and general shockwave configurations of MHD and non-MHD flow are also apparent. The solution is stable for Stuart number below 0.2. Conditional instability of the solver can be attributed to the MHD term’s contribution to the local speed of sound and can be avoided by taking it into account. The developed application has proven the suitability of the used schemes for resolving steep gradients in MHD supersonic flow problems. The study itself has shown theoretical possibility of studying the MHD flow control using OpenFOAM. Further research may include an effort to stabilize the solver and to enhance the mathematical model of the flow.

Numerical study on wall pressure over cone region of blunt-nosed body in high enthalpy shock tunnel HIEST

A cause of an overestimation of the computed surface pressure on a blunted cone in high-temperature hypersonic flow is explored. The overestimation was observed in a free-piston shock tunnel at the stagnation of H0=15.6 and 10.1 MJ/kg. The sensitivity analysis reveals that a reduction of the upstream translational temperature in the range of 100 to 300 K substantially improves the agreement of the surface pressure with the measured data. As the cause of the lower upstream translational temperature, radiative cooling effect is included in the thermochemical nonequilibrium calculation in the nozzle, the translational temperature at the nozzle exit is reduced to about 250 K. Using the obtained flow variables as the upstream boundary condition, the computed pressure agrees quite well with the experimental data. In order to clarify whether other variables such as translational–vibrational relaxation time, chemical reaction rates, and upstream chemical composition could be the cause of the discrepancy, uncertainty quantification is employed. It is shown that these parameters of the thermochemical model and upstream chemical composition have minor effect on the agreement of surface pressure. It is concluded that the observed discrepancy in the surface pressure is due to radiative cooling effect of high temperature gas in the nozzle region.

A “Laminar + Transition Criteria” Model for Hypersonic Three-Dimensional Boundary Layer Transition Prediction

A “laminar + transition criteria” model utilizingReθ/MeandReCFcriteria in conjunction with an intermittency functionΓis developed in this paper. With pretreated computational grid and total enthalpyh0=(h0,∞)maxcriteria the boundary layer edge and crossflow velocity can be obtained by using parallel methodology. Validation is accomplished via HIFiRE-5 and a blunt cone with small angle of attack. Results show that computedReθ/MeandReCFdistributions are similar to theN-factor for streamwise instability and crossflow instability from linear PSE methods. The shape and trend of transition regions predicted by the “laminar + transition criteria” model in HIFiRE-5 and blunt cone are in good agreement with the experiment and DNS. However, for the transition induced by inflection point on streamwise velocity profiles, using criteria related to boundary layer thickness is inappropriate and can predict transition onset prematurely.

Effect of AFM probe geometry on visco-hyperelastic characterization of soft materials

Atomic force microscopy (AFM) nanoindentation is very suited for nano- and microscale mechanical characterization of soft materials. Although the structural response of polymeric networks that form soft matter depends on viscous effects caused by the relative slippage of polymeric chains, the usual assumption made in the AFM-based characterization is that the specimen behaves as a purely elastic material and viscous forces are negligible. However, for each geometric configuration of the AFM tip, there will be a limit indentation rate above which viscous effects must be taken into account to correctly determine mechanical properties. A parametric finite element study conducted on 12 geometric configurations of a blunt cone AFM tip (overall, the study included about 200 finite element analyses) allowed us to determine the limit indentation rate for each configuration. The selected tip dimensions cover commercially available products and account for changes in tip geometry caused by serial measurements. Nanoindentation rates cover typical experimental conditions set in AFM bio-measurements on soft matter. Viscous effects appear to be more significant in the case of sharper tips. This implies that, if quantitative data on sample viscosity are not available, using a rounded indenter and carrying out experiments below the limit indentation rate will allow errors in the determination of mechanical properties to be minimized.

The Rapid Engineering Aero-Heating Calculation Method for Hypersonic Vehicles

The rapid engineering aero-heating calculation method for hypersonic vehicles is established for the question of computational efficiency during conceptual design stage. First the pressure distribution along vehicle’s surface is calculated by modified Newtonian theory. Secondly, the streamline along the surface is calculated with Newtonian steepest decent concept. Then by using reference enthalpy method, the heat flux on the surface is given. Finally, the heat flux on the surfaces of blunted cone, lifting body and wave-rider vehicle is calculated The analysis result shows the method used in this paper is fit for hypersonic vehicles, and can satisfies the aero-heating calculation during conceptual design stage in both efficiency and accuracy.

HYPERSONIC WIND TUNNEL FREE-FLIGHT TEST WITH BIPLANAR OPTICAL SYSTEM ON THE NON-SPINNING BLUNT CONE

To investigate the dynamic stability of the non-spinning blunt cone, wind-tunnel free-flight tests with biplanar optical system, were conducted at Mach 6 in the hypersonic wind tunnel. The tests show that coning motion appears for all the models,and in the range of viewing area the amplitude of angle of sideslip is larger than that of angle of attack, though only angle of attack is preset. For all the models, the amplitude of both angles of attack and sideslip is no more than 10 degree, while damping moment shows obvious nonlinearity and static moment exhibits approximate linearity. One of the models shows the tendency of limit planar motion or limit coning motion with small amplitude of angle of attack, others all tend to limit coning motion. End cover has little effect on the angular motion of the models, while the protuberance symmetrically placed on the model tail can affect the transformation of amplitude of angular motion, and the fluctuation of angular motion amplitude is obviously smaller for models with strake.

Large carbon cluster thin film gauges for measuring aerodynamic heat transfer rates in hypersonic shock tunnels

Different types of Large Carbon Cluster (LCC) layers are synthesized by a single-step pyrolysis technique at various ratios of precursor mixture. The aim is to develop a fast responsive and stable thermal gauge based on a LCC layer which has relatively good electrical conduction in order to use it in the hypersonic flow field. The thermoelectric property of the LCC layer has been studied. It is found that these carbon clusters are sensitive to temperature changes. Therefore suitable thermal gauges were developed for blunt cone bodies and were tested in hypersonic shock tunnels at a flow Mach number of 6.8 to measure aerodynamic heating. The LCC layer of this thermal gauge encounters high shear forces and a hostile environment for test duration in the range of a millisecond. The results are favorable to use large carbon clusters as a better sensor than a conventional platinum thin film gauge in view of fast responsiveness and stability.

A New Parallel Algorithm of DSMC Method

A new parallel algorithm of DSMC method with dynamic load balance implementation was introduced using MPI standard library. The parallel efficiency of the two kinds of parallel modes, peer-to-peer mode and master/slave mode, were investigated, respectively. The key points of implementation in unstructured DSMC code using peer-to-peer parallel mode were analyzed. Validity about this method was investigated by analyzing blunt cone flow field. The numerical results confirm the feasibility of method mentioned above.

Two-dimensional numerical analysis of flow ionization in the RAM-C-II flight experiment

The two-dimensional numerical analysis of experimental data on the degree of ionization of a compressed layer at the surface of a spacecraft shaped like a spherically blunted cone at a flight speed higher than 7 km/s at heights of 61–81 km is presented. The discussed data of a flight experiment were acquired within the framework of the RAM-C research project. A model of nonequilibrium physicochemical processes in a compressed layer behind the front of a leading shock wave, whose gas dynamics is described by Navier-Stokes equations, is considered. Different models of chemical kinetics were studied taking into account the processes of nonequilibrium dissociation and associative ionization. With the use of nonequilibrium dissociation models, the flight data on the concentration of electrons were adequately described not only under nearly equilibrium conditions but also under conditions without the thermalization of the internal degrees of freedom of the molecules of high-temperature air in a compressed layer.

Unsteady Vibration Aerodynamic Modeling and Evaluation of Dynamic Derivatives Using Computational Fluid Dynamics

Unsteady aerodynamic system modeling is widely used to solve the dynamic stability problems encountering aircraft design. In this paper, single degree-of-freedom (SDF) vibration model and forced simple harmonic motion (SHM) model for dynamic derivative prediction are developed on the basis of modified Etkin model. In the light of the characteristics of SDF time domain solution, the free vibration identification methods for dynamic stability parameters are extended and applied to the time domain numerical simulation of blunted cone calibration model examples. The dynamic stability parameters by numerical identification are no more than 0.15% deviated from those by experimental simulation, confirming the correctness of SDF vibration model. The acceleration derivatives, rotary derivatives, and combination derivatives of Army-Navy Spinner Rocket are numerically identified by using unsteady N-S equation and solving different SHV patterns. Comparison with the experimental result of Army Ballistic Research Laboratories confirmed the correctness of the SHV model and dynamic derivative identification. The calculation result of forced SHM is better than that by the slender body theory of engineering approximation. SDF vibration model and SHM model for dynamic stability parameters provide a solution to the dynamic stability problem encountering aircraft design.

Parallel Navier–Stokes simulations for high speed compressible flow past arbitrary geometries using FLASH

We report extensions to the FLASH code to enable high-speed compressible viscous flow simulation past arbitrary two- and three-dimensional stationary bodies. The body shape is embedded in a block-structured Cartesian adaptive mesh refinement grid by implementing appropriate computer graphics algorithms. A high mesh refinement level is required for an accurate body shape representation which results in large grid sizes especially for three-dimensional simulations. Simulations are done in parallel on IBM Blue Gene/Q computing system on which the code performance has been assessed in both pure MPI and hybrid MPI-OpenMP modes. We also implement appropriate wall boundary conditions in FLASH to model viscous-wall effects. Navier–Stokes (NS) solutions for various two-dimensional test cases like a shock–boundary layer interaction problem as well as for hypersonic flow past blunted cone–cylinder–flare and double-cone geometries are shown. Three dimensional NS simulations of micro vortex generators employed in hypersonic flow control have also been carried out and the computed results have been found to be consistent with experimental results.

Numerical Study of Hypersonic Boundary-Layer Receptivity with Freestream Hotspot Perturbations

This paper presents a numerical-simulation study of transient flow over a blunt compression cone under the effect of freestream hotspot perturbations. This study is motivated by concurrent wind-tunnel laser-spot experiments carried out at Purdue University. The flow conditions used in the simulation are based on the experimental conditions. The simulation is performed using a high-order shock-fitting finite-difference scheme. The simulation results show that the hotspot is able to excite second-mode instability, where the instability growth is found to be dominant in the boundary layer. The receptivity mechanism is investigated by comparing the simulated results with linear-stability theory. Fast acoustic waves generated by hotspot–shock interaction excite the boundary-layer disturbances. Also, the synchronization of mode F and mode S leads to the dominance of boundary-layer disturbances by the growing second mode.

Types of Antennal Sensilla of Three Pseudacteon Species (Diptera: Phoridae) Females That Parasitize Red Imported Fire Ants (Solenopsis invicta) ( Hymenoptera: Formicidae)

While antenna is the main organ for insect to accept the external chemical signals, the antennal sensilla that are diverse in structure and function form the insect receptors in chemical communication. Since a variety of Pseudacteon species are important natural enemies of the red imported fire ant, Solenopsis invicta Buren (. invicta), to elucidate the types of Pseudacteon sensilla will promote the study and understanding of the selection behavior of Pseudacteon in parasitizing . invicta. This study has used scanning electron microscope (SEM) to observe and investigate the female’s antennal sensilla of three Pseudacteon species, the Pseudacteon (P.) litoralis, P. obtusus, and P. tricuspis, and demonstrated that there are four types of sensilla, the trichoid, basiconic, coeloconic, and chaetic sensilla, on their antennal flagellum. Among them, the former three are common in all three species, with trichoid sensillum as mostly abundant, while the chaetic sensillum exists only in the antennae of P. obtusus. The trichoid sensilla exhibit significant interspecies variations and are further classified into two subtypes based on the presence or absence of protrusions, the surface of which contains different shades of groove-like or irregular punctate structures. The basiconic sensilla resemble short spines with densely porous structures on the surface and are in the length of 7.3-9.8 μm and the width of 1.3-1.6 μm, upright or slightly bent. The coeloconic sensilla are irregularly formed in the middle and base of the flagellum, without surface pores; each coeloconic sensillum has eight finger-like folds in unequal lengths, while the end of the fold resembles a blunt cone. The chaetic sensilla enlarge at the base, possess multiple fold-like structures and fine-tipped ends, and are approximately 5 μm in length.

An expression for the dynamic stability of blunt slender elliptic bodies in hypersonic flow

AbstractDynamic stability data on axially symmetric pointed and blunt cones, parabolic profiles and other ogive and blunt cylindrical shapes is readily available in literature; the dynamic stability on elliptic blunt paraboloids has not been studied at any great lengths in the past. Both numerical and experimental results are scarce. The present paper uses the shock expansion method to obtain the unsteady pressure distribution on blunt elliptic conical bodies at small angles-of-attack. The resulting unsteady pressure distribution is suitably integrated over the surface of the elliptic body to obtain appropriate analytic expressions for static and dynamic stability. Owing to scarcity of meaningful numerical or measured data for elliptic bodies, the results are compared in qualitative terms against published dynamic stability data on pointed elliptical cones or other axisymmetric blunt cones.

Research on Numerical Simulation of Support Interference for Dynamic Derivatives at Hypersonic Flight Speeds

The research on dynamic derivative under the dynamic unsteady condition is one of the most difficult aspects of the aircraft development process. For the special experiment of dynamic derivatives, no numerical simulation of support interference has yet been systematically studied. The numerical simulation of support interference for identification of dynamic derivatives with 7o blunted cone under the hypersonic condition was done in this paper. The 2-order Roe scheme and the dual-time-step method based on LU-SGS were respectively applied to discrete of the spatial and time derivative of the unsteady flow. A least square method based on the Etkin unsteady aerodynamic model was used for identification of dynamic derivatives. Hypersonic missile module was adopted as a verification example, and the numerical calculation results are consistent with the experimental results. For two different sting support forms with 7o blunted cone, the impact of sting support interference on dynamic derivatives was studied. Results show the moment coefficients of two support forms under static conditions are essentially the same, while there is a big difference in the pitch damping derivatives under dynamic conditions. The support interference of nonlinear aerodynamic loads resulted from the shock wave induced separation and other unsteady flow structures under dynamic conditions is far more complicated than that under static conditions, and the correction law of support interference under static conditions cannot be applied directly to the unsteady dynamic situations.