Navier-Stokes, flight, and wind tunnel flow analysis for the F/A-18 aircraft

Computational analysis of flow over the F/A-18 aircraft is presented along with complementary data from both flight and wind tunnel experiments. The computational results are based on the three-dimensional thin-layer Navier-Stokes formulation and are obtained from an accurate surface representation of the fuselage, leading-edge extension (LEX), and the wing geometry. However, the constraints imposed by either the flow solver and/or the complexity associated with the flow-field grid generation required certain geometrical approximations to be implemented in the present numerical model. In particular, such constraints inspired the removal of the empennage and the blocking (fairing) of the inlet face. The results are computed for three different free-stream flow conditions and compared with flight test data of surface pressure coefficients, surface tuft flow, and off-surface vortical flow characteristics that included breakdown phenomena. Excellent surface pressure coefficient correlations, both in terms of magnitude and overall trend, are obtained on the forebody throughout the range of flow conditions. Reasonable pressure agreement was obtained over the LEX; the general correlation tends to improve at higher angles of attack. The surface tuft flow and the off-surface vortex flow structures compared qualitatively well with the flight test results. To evaluate the computational results, a wind tunnel investigation was conducted to determine the effects of existing configurational differences between the flight vehicle and the numerical model on aerodynamic characteristics. In most cases, the geometrical approximations made to the numerical model had very little effect on overall aerodynamic characteristics

Intelligent Systemic/Systematic Innovation and Its Role in Delivering Improvement and Change in the Design of Mission Critical Systems

Mission critical systems (MCS) are complex nested hierarchies of systems, subsystems and components with defined purpose, characteristics, boundaries and interfaces, working in harmony to deliver vital organisational functionalities. Upgrading MCS performance is inevitable when capability enhancement is required or new technologies emerge. Improving MCS however is considered with certain degrees of reluctance due to their sensitive role in organisations and the potential disruptive impact of unexpected consequences of change. Innovation in MCS often appears in small steps that affect the entire system due to their highly interdependent structures. Effective management of innovation introduction in complex systems require systemic/systematic processes that involve process management and collective analysis, scoping, decision-making and R&D which relies on effective information sharing. This approach should run throughout the system and must include all aspects and stakeholders, utilising the skills and knowledge of all involved. This chapter describes the basic concepts and potential approaches that could be utilised to build intelligent systemic/systematic and collaborative environments for MCS innovation. Advances in ICT technologies provide an opportunity to access the wider sphere of knowledge and support the systemic innovation processes. Adopting systemic approaches increases process efficacy, leading to more reliable solutions, shorter development lead times and reduced costs

Margin Changes Effects of Price and Return Volatility in Gold Coin Futures Market at Iran Mercantile Exchange

Supervisory institutes have paid a great attention to the use of margin as a control tool of excessive speculation in futures contracts market. Therefore, this paper studied margin changes effects on price and price volatility in Iran Mercantile Exchange (hereafter IME) using gold coin futures contracts data from November 2008 to July 2014. The US commodity futures trading commission (henceforth CFTC) has the authority to increase the margin to control speculators activities and prices in future contracts market. According to our research, based on information garnered from futures contracts market of Bahar-e-Azadi gold coin in IME, we concluded that any increase in margin results in higher open position costs, which begets price ascend. Considering our results, more amount of margin begets speculator providing liquidity out of the market, consequently surges price volatility. However, the results showed that there is no significant difference between effects of increased and decreased margins. Unfavorably, the effect of considerable margin change was smaller than that of small ones

Detached Eddy Simulation Results for a Space Launch System Configuration at Liftoff Conditions and Comparison with Experiment

Computational simulations for a Space Launch System configuration at liftoff conditions for incidence angles from 0 to 90 degrees were conducted in order to generate integrated force and moment data and longitudinal lineloads. While the integrated force and moment coefficients can be obtained from wind tunnel testing, computational analyses are indispensable in obtaining the extensive amount of surface information required to generate proper lineloads. However, beyond an incidence angle of about 15 degrees, the effects of massive flow separation on the leeward pressure field is not well captured with state of the art Reynolds Averaged Navier-Stokes methods, necessitating the employment of a Detached Eddy Simulation method. Results from these simulations are compared to the liftoff force and moment database and surface pressure data derived from a test in the NASA Langley 14- by 22-Foot Subsonic Wind Tunnel

Error Estimate of the Ares I Vehicle Longitudinal Aerodynamic Characteristics Based on Turbulent Navier-Stokes Analysis

Numerical predictions of the longitudinal aerodynamic characteristics for the Ares I class of vehicles, along with the associated error estimate derived from an iterative convergence grid refinement, are presented. Computational results are based on the unstructured grid, Reynolds-averaged Navier-Stokes flow solver USM3D, with an assumption that the flow is fully turbulent over the entire vehicle. This effort was designed to complement the prior computational activities conducted over the past five years in support of the Ares I Project with the emphasis on the vehicle s last design cycle designated as the A106 configuration. Due to a lack of flight data for this particular design s outer mold line, the initial vehicle s aerodynamic predictions and the associated error estimates were first assessed and validated against the available experimental data at representative wind tunnel flow conditions pertinent to the ascent phase of the trajectory without including any propulsion effects. Subsequently, the established procedures were then applied to obtain the longitudinal aerodynamic predictions at the selected flight flow conditions. Sample computed results and the correlations with the experimental measurements are presented. In addition, the present analysis includes the relevant data to highlight the balance between the prediction accuracy against the grid size and, thus, the corresponding computer resource requirements for the computations at both wind tunnel and flight flow conditions. NOTE: Some details have been removed from selected plots and figures in compliance with the sensitive but unclassified (SBU) restrictions. However, the content still conveys the merits of the technical approach and the relevant results

Consumer rights in Iran’s telecom: Investigation effective drivers on permission base mobile marketing

Nowadays the SMS advertisements in Iran are sent without observing the regulations which protect the consumer rights; this practice has proved to be a major annoyance to Iranian mobile users. In this paper, the factors which need to be examined before gaining mobile user’s permission were evaluated. The hypothesized model is empirically tested using data collected from a survey in Tehran theater-e-shahr audiences. Structural Equation Modeling (SEM) was used to evaluate the causal model and Confirmatory Factor Analysis (CFA) was performed to examine the reliability and validity of the measurement model. It is concluded that mobile marketing experience extremely affects the process of getting mobile users’ permission

Consumer rights in Iran’s telecom: Investigation effective drivers on permission base mobile marketing

Nowadays the SMS advertisements in Iran are sent without observing the regulations which protect the consumer rights; this practice has proved to be a major annoyance to Iranian mobile users. In this paper, the factors which need to be examined before gaining mobile user’s permission were evaluated. The hypothesized model is empirically tested using data collected from a survey in Tehran theater-e-shahr audiences. Structural Equation Modeling (SEM) was used to evaluate the causal model and Confirmatory Factor Analysis (CFA) was performed to examine the reliability and validity of the measurement model. It is concluded that mobile marketing experience extremely affects the process of getting mobile users’ permission

Turbulent Vortex-Flow Simulation Over a 65 deg Sharp and Blunt Leading-Edge Delta Wing at Subsonic Speeds

Turbulent thin-layer, Reynolds-Averaged Navier-Stokes solutions, based on a multi-block structured grid, are presented for a 65 deg delta wing having either a sharp leading edge (SLE) or blunt leading edge (BLE) geometry. The primary objective of the study is to assess the prediction capability of the method for simulating the leading-edge flow separation and the ensuing vortex flow characteristics. Computational results are obtained for two angles of attack of approximately 13 and 20 deg, at free-stream Mach number of 0.40 and Reynolds number of 6 million based on the wing mean aerodynamic chord. The effects of two turbulence models of Baldwin-Lomax with Degani-Schiff (BL/DS) and the Spalart-Allmaras (SA) on the numerical results are also discussed. The computations also explore the effects of two numerical flux-splitting schemes, i.e., flux difference splitting (fds) and flux vector splitting (fvs), on the solution development and convergence characteristics. The resulting trends in solution sensitivity to grid resolution for the selected leading-edge geometries, angles of attack, turbulence models and flux splitting schemes are also presented. The validity of the numerical results is evaluated against a unique set of experimental wind-tunnel data that was obtained in the National Transonic Facility at the NASA Langley Research Center

Kestrel Results at Liftoff Conditions for a Space Launch System Configuration in Proximity to the Launch Tower

Aerodynamic data books for Space Launch System vehicles require databases for the integrated forces and moments and section loads during liftoff and transition to the ascent phase of flight. While the force and moment database can be generated from wind tunnel results, computational analyses are necessary to provide the extensive surface information required to generate proper lineloads. Of the two flight regimes, the liftoff problem is the more costly and complex situation to simulate, as it requires modeling of the vehicle in proximity to the launch tower. The effects of massive separation on the leeward pressure fields of both the tower and vehicle are not well captured with RANS methods, necessitating the use of more advanced methods, such as Delayed Detached Eddy Simulation, in conjunction with computational grids sufficiently refined to resolve the wakes. Details on the computational setup for employing the Kestrel flow solver to address the liftoff problem are presented. The methodology involves the use of independent unstructured near-body grids for the vehicle and the tower, overset by a solution adaptive Cartesian off-body grid. Results from the simulations are compared to experime ASA Langley Research Center 14- by 22-Foot Subsonic Tunnel