Prediction Of Pressure Distribution Research Articles

Drying of granular medium by hot air and microwaves. Modeling and prediction of internal gas pressure and binder distribution

With the aim of enhancing the industrial drying (hot air and microwaves) of inserts made of agglomerated sand and to assess product quality, a comprehensive internal heat and mass transfer model has been proposed. In this model, liquid and vapor transfer by filtration, liquid expulsion at the surface and binder transfer by advection were directly accounted for. This model was validated on the basis of the experimental average water and binder content and core temperature curves for drying trials at different operating conditions. Then, it was used for comparing the drying time, the internal pressure and the binder content calculated for several test processes. It was demonstrated that the simultaneous application of hot air and micro-waves provided a real possibility to dry faster and to maintain quite the same internal overpressure and overall binder content as for the reference (damage free) process. The heating power should be increased gradually during the process. The decrease of the drying time was around 30% with regard to the reference mild process.

A Panel Method with a Full Wake Alignment Model for the Prediction of the Performance of Ducted Propellers

An improved perturbation potential‐based panel method is applied to model the flow around ducted propellers. One significant development in this method is the application of full wake alignment scheme in which the trailing vortex wake sheets of the blades are aligned with the local flow velocity by also considering the effects of duct and duct wake. A process of repaneling the duct is simultaneously introduced to improve the accuracy of the method. The results from the improved wake model are compared with those from a simplified wake alignment scheme. At the same time, full-blown Reynolds-averaged Navier‐Stokes (RANS) simulations are conducted via commercial solvers. The forces, i.e., thrust and torque, on the propeller predicted by this panel method under the improved wake alignment model show good agreement both with experimental measurements, a hybrid method developed by the Ocean Engineering Group of University of Texas at Austin, and the full-blown RANS simulations. Moreover, predicted pressure distribution on the blades and duct are compared among the various methods.

A Panel Method with a Full Wake Alignment Model for the Prediction of the Performance of Ducted Propellers

An improved perturbation potential-based panel method is applied to model the flow around ducted propellers. One significant development in this method is the application of full wake alignment scheme in which the trailing vortex wake sheets of the blades are aligned with the local flow velocity by also considering the effects of duct and duct wake. A process of repaneling the duct is simultaneously introduced to improve the accuracy of the method. The results from the improved wake model are compared with those from a simplified wake alignment scheme. At the same time, full-blown Reynolds-averaged Navier-Stokes (RANS) simulations are conducted via commercial solvers. The forces, i.e., thrust and torque, on the propeller predicted by this panel method under the improved wake alignment model show good agreement both with experimental measurements, a hybrid method developed by the Ocean Engineering Group of University of Texas at Austin, and the full-blown RANS simulations. Moreover, predicted pressure distribution on the blades and duct are compared among the various methods.

A Solution Adaptive Cartesian Grid Based Euler Solution for Compressible Flow Around BOEING TR-1322 Multi-element Airfoil

Cartesian grids constitute a special branch in unstructured grid technology. They use specially designed algorithms to generate automatic grids for complex geometries and to simulate flows around such geometries regardless of the body shape and number of bodies. Cartesian grids are generated by constructing a quadtree based data structure for the purpose of connecting the Cartesian cells to each other. A “hands-off”, Cartesian grid generator based Euler solution called GeULER is implemented in object-oriented FORTRAN programming language. In this study, implementations of generated two-dimensional adaptive refinement/coarsening scheme codesare appended to the developed compressible flow solver by using special Cartesian-based algorithms, namely cut-cell adaptation and curvature adaptation around BOEING TR-1322 multi-element airfoil. A subsonic flow at free stream Mach number of 0.11 around the airfoil is tested to predict pressure distributions around it and Mach contours of the flow are depicted by using the developed GeULER code.

Numerical Analysis of Flow Over the NASA Common Research Model Using the Academic Computational Fluid Dynamics Code Galatea

A recently developed academic computational fluid dynamics (CFD) code, named Galatea, is used for the computational study of fully turbulent flow over the NASA common research model (CRM) in a wing-body configuration with and without horizontal tail. A brief description of code's methodology is included, while attention is mainly directed toward the accurate and efficient prediction of pressure distribution on wings' surfaces as well as of computation of lift and drag forces against different angles of attack, using an h-refinement approach and a parallel agglomeration multigrid scheme. The obtained numerical results compare close with both the experimental wind tunnel data and those of reference solvers.

Semi-empirical prediction of internal pressure distribution and muzzle velocity in the rifled barrel of a light weapon

When a weapon is fired, pressure that dynamically changes behind the projectile/bullet and along the barrel and the projectile velocity are the most important internal ballistic parameters for barrel design. These facts require time consuming and expensive measurements, knowledgeable personnel and additional safety measures to properly study. In this work, shooting tests were conducted extensively for different projectile and gunpowder weights using NATO standard small caliber barrels of 7.62mm and 5.56mm in diameter. Internal pressure distributions and projectile velocities were measured as functions of time and displacement experimentally. Using the curve-fitting method, a projectile velocity profile was modeled according to a function defined as v(x)=axk(xk+b) and the barrel internal pressure was derived from the velocity profile. The coefficients a, b and k were determined empirically based on projectile and gunpowder weights. The model was validated for various barrel lengths using a custom-designed barrel. With the velocity function defined in this work, the internal pressure distributions and projectile velocities of 7.62mm and 5.56mm small caliber weapons were predicted within 90% of confidence without the need for time consuming and expensive measurements.

Predicting pressure distribution between transfemoral prosthetic socket and residual limb using finite element analysis

A static implicit nonlinear finite element model (FEM) was created and analysed to determine the pressure distribution between the residual limb and the prosthetic socket of a transfemoral amputee. This analysis was performed in an attempt to develop a process allowing healthcare providers and engineers to simulate the fit and comfort of transfemoral prosthetics to reduce the number of re-fittings. The FEM considered the effects of donning and body weight and included geometric nonlinearity due to large deflections, nonlinear contacts due to friction, and nonlinear hyper-elastic material properties for the residual limb's soft tissue. The results attained can provide prosthetic fitting clinicians customised information on where the prosthetic fits too tight, and how stress concentrations would change as a result of geometric modifications to the prosthetic. This knowledge can improve patients' comfort levels by providing well targeted and more accurate modifications to the prosthetic, minimising the need for numerous refittings.

A chemo-mechanical coupling model of deviated borehole stability in hard brittle shale

Abstract A chemo-mechanical coupling model of borehole stability in hard brittle shale considering structure characteristics and targeted hydration was established, the influencing factors of the distribution of collapse pressure were analyzed based on the model, and a field case analysis was conducted. Based on the physicochemical properties of hard brittle shale, a drilling fluid activity window was proposed for calculating collapse pressure by establishing the relationships of drilling fluid activity vs. swelling ratio of rock and rock activity vs. moisture content to determine critical swelling ratio of rock and reasonable moisture content. The results show that, when fixing the dip angle of weak plane, the collapse pressure appears a quarter symmetric distribution with the change in tendency, there is no azimuth angle who has a monotonic increasing or decreasing collapse pressure, and dangerous sections and safe sections exist alternately; compared with cohesion of weak plane, collapse pressure is more sensitive to internal friction angle. Field case shows that, accurate prediction of collapse pressure distribution can be obtained by the chemo-mechanical coupling model, in which borehole stability can be ensured and the density of drilling fluid can be decreased as long as the drilling fluid activity is controlled in the window.

Prediction of pressure distribution between the vocal folds using Bernoulli’s equation

Determining the mechanisms of self-sustained oscillation of the vocal folds requires characterization of intraglottal aerodynamics. Since most of the intraglottal aerodynamics forces cannot be measured experimentally, most of the current understanding of vocal fold vibration mechanism is derived from analytical and computational models. Several of such studies have used the Bernoulli’s equation in order to calculate the pressure distribution between the vibrating folds. In the current study, intraglottal pressure measurements are taken in a hemilarynx model and are compared with pressure values that are computed form the Bernoulli’s equation. The hemilarynx model was made by removing one fold and having the remaining fold vibrating against a metal plate. The plate was equipped with two pressure ports located near the superior and inferior aspects of the fold. The results show that pressure calculated using Bernoulli’s equation matched well with the measured pressure waveform during the glottal opening phase and dissociated during the closing phase.

Two relaxation time lattice Boltzmann equation for high Knudsen number flows using wall function approach

In the present study, we investigate gas flow in a micro-/nanochannel by using the two relaxation time lattice Boltzmann equation (TRT-LBE). The wall function approach is employed in order to consider the effect of Knudsen layer in transition flow regime. In this context, two different wall functions called power law and exponential functions are applied to pressure-driven gas flow through a micro-/nanochannel. Also, the slip velocity is realized by defining a relation between the relaxation times of the model. The advantage of the present approach over previous slip boundary conditions is ease of implementation. The TRT-LBE used in this study is comparable with the single relaxation time (SRT) model in simplicity and computational cost, but the additional relaxation time enables the model to treat the slip velocity more accurately. In the results section, we evaluate our model against direct simulation Monte Carlo (DSMC), information preservation (IP) and linearized Boltzmann solution. The accuracy of power law and exponential functions in prediction of velocity profiles, pressure distribution and mass flow rate is also investigated. The results show that the TRT-LBE using wall function correction can satisfactorily predict the flow behavior up to the upper end of the transition flow regime.

Optimal Machine-Tool Settings for the Manufacture of Face-Hobbed Spiral Bevel Gears

In this study, an optimization methodology is proposed to systematically define the optimal head-cutter geometry and machine-tool settings to simultaneously minimize the tooth contact pressure and angular displacement error of the driven gear (the transmission error), and to reduce the sensitivity of face-hobbed spiral bevel gears to the misalignments. The proposed optimization procedure relies heavily on the loaded tooth contact analysis for the prediction of tooth contact pressure distribution and transmission errors influenced by the misalignments inherent in the gear pair. The load distribution and transmission error calculation method employed in this study were developed by the author of this paper. The targeted optimization problem is a nonlinear constrained optimization problem, belonging to the framework of nonlinear programming. In addition, the objective function and the constraints are not available analytically, but they are computable, i.e., they exist numerically through the loaded tooth contact analysis. For these reasons, a nonderivative method is selected to solve this particular optimization problem. That is the reason that the core algorithm of the proposed nonlinear programming procedure is based on a direct search method. The Hooke and Jeeves pattern search method is applied. The effectiveness of this optimization was demonstrated on a face-hobbed spiral bevel gear example. Drastic reductions in the maximum tooth contact pressure (62%) and in the transmission errors (70%) were obtained.

Application of Finite Element Method for Modeling of Multi-tube Fixed Bed Catalytic Reactors

Abstract In this article, the finite element method (FEM) was applied for modeling of multi-tube fixed bed catalytic reactor (FBCR). For this purpose, a more sophisticated 2D pseudo-heterogeneous model was used to calculate steady-state temperature and partial pressure profiles through the reactor. This model has a vast capability in the prediction of temperature and partial pressure distribution, separately, in the fluid and catalyst phases. The finite element results were compared with de wasch and Froment’s numerical work which developed for a well-established reaction in the multi-tube FBCR (o-xylene partial oxidation). The R-squared analysis indicated that the FEM results agree favorably with finite difference results which reported in the literature. Numerical solution coincidence of FEM and FDM increases with reduction of inlet gas temperature. The results show that the finite element as a powerful numerical method can be used to describe the multi-tube fixed bed catalytic reactor.

Ignition Transients in a Scramjet Engine with Air Throttling Part II: Reacting Flow

The analysis presented in Part I of this study is extended to investigate ignition transients and flame development in an ethylene-fueled scramjet engine. Unheated gaseous ethylene is transversely injected into the combustor upstream of a recessed cavity flameholder. Immediately after the ethylene–air mixture reaches its steady state in the combustor, a hotspot igniter is activated in the cavity to initiate chemical reactions. Cases both with and without air throttling downstream of the cavity during the engine startup stage are examined in detail. Successful ignition can only be achieved with the aid of air throttling under the present flow conditions. As a consequence of the backpressurization by the throttling air, a shock train is generated in the isolator, which then decelerates the high-speed main stream, enhances the fuel mixing efficiency, and increases the temperature and pressure in the combustor. Chemical reactions are intensified and produce sufficient heat release to maintain a flow environment conducive to flame stabilization. A self-sustaining mechanism is thus established between the flow and flame development. Stable flames are achieved even after the deactivation of air throttling. The predicted pressure distribution along the entire flowpath agrees well with experimental measurements.

Prediction Model of Pressure Distribution under Floating Strips

The accuracy prediction of the strip's upper pressure and lower pressure is very important to the accuracy control of air flotation oven, therefore the aluminum can get high surface quality and improving the product quality. And the pressure prediction is very important factor in air flotation oven. In this paper, pso-lssvm pressure prediction model was established. The experiment was carried out in an experimental air flotation oven and pressure data was collected, then the pso-lssvm model was trained based on the training data. The pso-lssvm pressure model' result was compared with the experimental value. The experimental result shows that the pso-lssvm model can get higher accuracy and is suited to predict pressure distribution.

Optimization of face-hobbed hypoid gears

In this study, an optimization methodology is presented to systematically define head-cutter geometry and machine tool settings to introduce optimal tooth modifications in face-hobbed hypoid gears. The goal of the optimization is to simultaneously minimize tooth contact pressures and angular displacement error of the driven gear (the transmission error), while concurrently confining the loaded tooth contact pattern within the tooth boundaries and avoiding any edge- or corner-contact conditions. The proposed optimization procedure relies heavily on the loaded tooth contact analysis for the prediction of tooth contact pressure distribution and transmission errors developed by the author of this paper. The targeted optimization problem is a nonlinear constrained optimization problem, belonging to the framework of nonlinear programming. In addition, the objective function and the constraints are not available analytically, but they are computable, i.e., they exist numerically through the loaded tooth contact analysis. For these reasons, a nonderivative method is selected to solve this particular optimization problem. The effectiveness of this optimization was demonstrated by using a face-hobbed hypoid gear example. Considerable reductions in the maximum tooth contact pressure and in the transmission errors were obtained.

Applications of different turbulence models in simulations of a large annular volute-type pump with the diffuser

It's necessary to choose a good turbulence model for the reliable numerical simulation of the pump in hydraulic optimization. In this paper, the four widely used turbulence models are selected and compared in three dimensional steady numerical simulations for a large annular volute-type pump with the diffuser. The pump performance is verified by the experiments in an open test rig. The results show that the SST turbulence model gets closer values to the experiment in predicting head. The trend of the pressure distribution at design condition for the four models on pressure side is very similar, which first increases and then decreases along the streamline. There are a minimum at 0.05 and a maximum at 0.8 of the length of the streamline, due to the existence of vortices. The predicted pressure distribution on the suction side is more similar. With the increase of flow rate, the flow field in the impeller becomes more uniform, and the number as well as the size of the vortices decrease. Secondary flow is observed in the volute and three vortices are found near the upside of the volute.

Theoretical Study of Direct Steam Generation in Two Parallel Pipes

In this work it was simulated the direct steam generation (DSG) in a system of two horizontal parallel pipes by using the commercial simulator RELAP. The pipes were 500 m long, internal diameter 5cm, and wall thickness of 10mm. Pipes were fed with sub-cooled water and the output can be: 1) hot water, 2) a steam-water mixture, 3) overheated steam. The flow was at steady state and pipes were undergoing to uniform and concentrated solar heating. Moreover, the effect of symmetric and asymmetric heating, on the DSG process, was studied.RELAP code allowed predicts flow distribution and inlet pressure. Predictions of inlet pressure and flow distribution were compared against predictions from literature. The pressure drop calculated by RELAP presented good fitting with field data from the Plataforma Solar de Almería (PSA).The study of flow distribution showed that RELAP is able to get the most stable solutions. It was found that for symmetric solar heating, asymmetric flow distribution solutions may be present in the system. Moreover, for asymmetric heating the mass flow rate is larger in the pipe with smaller heating. This is an unfavorable condition under a practical point of view. The concentrated solar heating does not affect in a considerable way the flow distribution in relation to the uniform solar heating; however, it could affect the flow pattern transition along the pipe (s).

Applying Method of Characteristics to Determine Pressure Distribution in 1D Shale-Gas Samples

SummaryThis paper examines application of the method of characteristics (MOC) to determine pressure distribution in a 1D matrix of shale gas. Because of gas expansion and local desorption in shale gas, pressure distribution changes during production. We developed a semianalytic MOC solution of gas flow in shale by use of the analogous-continuum approximation (apparent permeability). The MOC solution is derived with the inclusion of compressibility, gas-slippage effect, and desorption.Through quantitative comparison of pressure profiles and history plots, we used a simulation approach to verify the accuracy of the analytic solution. Results suggest that the simulation results are consistent with our MOC solution, which can also be used to evaluate impacts of different parameters on pressure distribution. Prediction of pressure distribution over time will greatly enhance approximation of reservoir performance.

Optimal Tooth Surface Modifications in Face-Hobbed Hypoid Gears

In this study, an optimization methodology is proposed to systematically define head-cutter geometry and machine tool settings to introduce optimal tooth modifications in face-hobbed hypoid gears. The goal of the optimization is to simultaneously minimize tooth contact pressures and angular displacement error of the driven gear, while concurrently confining the loaded contact pattern within the tooth boundaries. The proposed optimization procedure relies heavily on a loaded tooth contact analysis for the prediction of tooth contact pressure distribution and transmission errors. The objective function and the constraints are not available analytically, but they are computable, i.e., they exist numerically through the loaded tooth contact analysis. The core algorithm of the proposed nonlinear programming procedure is based on a direct search method. Effectiveness of this optimization was demonstrated by using a face-hobbed hypoid gear example. Considerable reductions in the maximum tooth contact pressure and in the transmission errors were obtained.

LIQUID–LIQUID MIXTURES FLOW IN MICROCHANNELS

This study constitutes an experimental and numerical investigation into the single-phase flow of liquid–liquid mixtures and of water in uniform, converging and diverging microchannels. The experimental results for the pressure drop in three microchannels show good agreement with both theoretical predictions and CFD simulation results. The numerical velocity profiles in microchannels are also presented and show excellent agreement with the analytical velocity profiles. In addition, the pressure distribution prediction for the converging and diverging microchannels is also consistent with that obtained through the CFD results.