scholarly journals Desenvolvimento de um modelo numérico para a predição de um escoamento em bocal do tipo H.O.M.E.R

2019 ◽  
Vol 5 (1) ◽  
pp. 129-137
Author(s):  
Elizaldo Domingues dos Santos
Keyword(s):  
High Speed ◽  
Navier Stokes ◽  
Reynolds Averaged Navier Stokes

No presente estudo é desenvolvido um modelo numérico para a abordagem de escoamentos turbulentos no regime permanente em bocais do tipo H.O.M.E.R (do inglês: High-speed Orienting Momentum with Enhanced Reversibility) que consiste na mistura de dois jatos incidentes sobre superfícies de Coanda. Essa superfície causa uma deflexão no escoamento permitindo que o bocal atue como um dispositivo de manobra em aplicações aeronáuticas. O principal objetivo é avaliar o modelo numérico desenvolvido comparando com resultados numéricos da literatura. As equações de conservação de massa e quantidade de movimento médias no tempo são resolvidas numericamente através do método de volumes finitos. Para resolver o problema do fechamento da turbulência foi empregada modelagem clássica (RANS – do inglês: Reynolds Averaged Navier Stokes) com modelo k – ε. Primeiramente, um teste de independência de malha será realizado, com o intuito de dispender menos recursos computacionais e obter resultados precisos. Em seguida, serão feitas as simulações em regime permanente, com o objetivo de obter os ângulos de deflexão (α) gerados com a diferença das vazões mássicas injetadas em cada um dos canais do bocal H.O.M.E.R (m*). Posteriormente, esses resultados são comparados com os obtidos numericamente na literatura. Os resultados obtidos tiveram o mesmo comportamento obtido na literatura, onde o aumento da diferença entre os jatos de entrada conduziu a um aumento no ângulo de deflexão do jato no bocal. Com exceção de um valor específico (m* = 0.2) os resultados obtidos no presente trabalho apresentaram uma boa concordância com os preditos numericamente na literatura.

Reynolds-averaged Navier–Stokes simulation of hydrofoil effects on hydrodynamic coefficients of a catamaran in forced oscillation

2016 ◽  
Vol 231 (2) ◽  
pp. 364-383
Author(s):  
Amin Najafi ◽  
Mohammad Saeed Seif
Keyword(s):  
High Speed ◽  
Experimental Approach ◽  
Navier Stokes ◽  
Hydrodynamic Coefficients ◽  
Laboratory Equipment ◽  
Factors Affecting ◽  
High Frequencies ◽  
Frequency Independent ◽  
Reynolds Averaged Navier Stokes

Determination of high-speed crafts’ hydrodynamic coefficients will help to analyze the dynamics of these kinds of vessels and the factors affecting their dynamic stabilities. Also, it can be useful and effective in controlling the vessel instabilities. The main purpose of this study is to determine the coefficients of longitudinal motions of a planing catamaran with and without a hydrofoil using Reynolds-averaged Navier–Stokes method to evaluate the foil effects on them. Determination of hydrodynamic coefficients by experimental approach is costly and requires meticulous laboratory equipment; therefore, utilizing the numerical methods and developing a virtual laboratory seem highly efficient. In this study, the numerical results for hydrodynamic coefficients of a high-speed craft are verified against Troesch’s experimental results. In the following, after determination of hydrodynamic coefficients of a planing catamaran with and without foil, the foil effects on its hydrodynamic coefficients are evaluated. The results indicate that most of the coefficients are frequency-independent especially at high frequencies.

Calculation of Debris Trajectories During High-Speed Snowplowing

2002 ◽  
Author(s):  
H. K. Nakhla ◽  
B. E. Thompson
Keyword(s):  
Particle Tracking ◽  
High Speed ◽  
Turbulence Modeling ◽  
Stokes Equations ◽  
Cutting Edge ◽  
Navier Stokes ◽  
Engineering Model ◽  
Navier Stokes Equations ◽  
Snow Plowing ◽  
Reynolds Averaged Navier Stokes

An engineering model is presented to calculate the trajectory of airborne debris that adversely affects visibility during high-speed snow plowing. Reynolds-averaged Navier-Stokes equations are solved numerically with turbulence-modeling, particle-tracking, and cutting-edge approximations. Results suggest snow can be divided into splash and snow-cloud when designing treatments to improve visibility for snowplow drivers and following traffic. Calculated results confirm the findings of windtunnel and road tests, specifically that the trap angle of overplow deflectors should be less than 50 degrees to eliminate snow debris blowing over top of the plow onto the windscreen.

Reynolds-Averaged Navier-Stokes Simulations for High-Speed Wigley Hull in Deep and Shallow Water

2007 ◽  
Vol 51 (03) ◽  
pp. 187-203
Author(s):  
Nobuaki Sakamoto ◽  
Robert Vance Wilson ◽  
Frederick Stern
Keyword(s):  
Shallow Water ◽  
Message Passing ◽  
High Speed ◽  
High Performance ◽  
Message Passing Interface ◽  
Iterative Solvers ◽  
Verification And Validation ◽  
Navier Stokes ◽  
Wigley Hull ◽  
Reynolds Averaged Navier Stokes

Reynolds-averaged Navier-Stokes simulations and verification and validation studies for a high-speed Wigley hull in deep and shallow water are presented using CFD-SHIP-IOWA Version 4.00, which is a general-purpose ship hydrodynamics computational fluid dynamics code: single-phase level set free surface and k-w turbulence modeling; higher-order conservative discretization, embedded overset grids, advanced iterative solvers, and implicit coupling flow field and predicted motions numerical methods; and high-performance computing for message-passing interface (MPI)-based domain decomposition. The results are presented for low to high speed and deep to shallow water. The investigation is exploratory in nature using an idealized geometry and relatively coarse grids. Based on the verification and validation results, modifications for increased grid resolution at the bow for high speed and improved grid orthogonality for shallow water are made to obtain better solutions. The flow physics observations provide both integral and differential views of the highspeed and shallow-water flow fields, including resistance, pressure variation, wave pattern, boundary layer, and vortices.

The Evolution of Computational Methods in Aerodynamics

1983 ◽  
Vol 50 (4b) ◽  
pp. 1052-1070 ◽  
Author(s):  
A. Jameson
Keyword(s):  
Euler Equations ◽  
Computational Methods ◽  
High Speed ◽  
Stokes Equations ◽  
Inviscid Flow ◽  
Flow Equation ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Electronic Computers ◽  
Reynolds Averaged Navier Stokes

This paper surveys the evolution of computational methods in aerodynamics. Improvements in high-speed electronic computers have made it feasible to attempt numerical calculations of progressively more complex mathematical models of aerodynamic flows. Numerical approximation methods for a hierarchy of models are examined in ascending order of complexity, ranging from the linearized potential flow equation to the Reynolds averaged Navier Stokes equations, with the inclusion of some previously unpublished material on implicit and multigrid methods for the Euler equations. It is concluded that the solution to the Euler equations for inviscid flow past a complete aircraft is a presently attainable objective, while the solution to the Reynolds averaged Navier Stokes equations is a possibility clearly visible on the horizon.

scholarly journals Analisa Bentuk Foil pada Kapal Hydrofoil Supported-Catamaran (Hysucat)

2020 ◽  
Vol 4 (3) ◽  
pp. 145-156
Author(s):  
Yokhebert Natasya Siahaan ◽  
Samuel Samuel ◽  
Berlian Arswendo Adietya
Keyword(s):  
Fluid Flow ◽  
Numerical Method ◽  
High Speed ◽  
Lift Force ◽  
Water Phase ◽  
Navier Stokes ◽  
Hull Form ◽  
Reynolds Averaged Navier Stokes ◽  
Two Phases ◽  
Method Approach

ABSTRAKKapal katamaran yang terintegrasi dengan foil bertujuan untuk menghasilkan performance lebih baik. Hydrofoil Supported-Catamaran (Hysucat) merupakan kapal katamaran yang dirancang untuk kecepatan tinggi menggunakan foil. Penelitian ini dilakukan dengan pendekatan metode numerik untuk mempresentasikan aliran fluida menggunakan RANS (Reynolds-Averaged Navier-Stokes). Aliran fluida pada penelitian ini menggunakan dua fasa yaitu air dan udara untuk menganalisis hambatan dan gaya angkat kapal katamaran yang telah dimodifikasi menjadi hysucat. Hysucat pada penelitian ini dibedakan oleh tiga macam bentuk foil yaitu lurus, sweep belakang dan sweep depan dengan tambahan variasi pada chord line dan sudut serang foil. Penambahan foil pada penelitian ini memberikan informasi bahwa hysucat dengan bentuk foil sweep belakang chord line 1.2 dan AOA(sudut serang) 0º mengurangi hambatan kapal sebesar 21% dari hambatan kapal katamaran tanpa foil. Gaya angkat tertinggi dihasilkan hysucat dengan bentuk foil sweep belakang chord line 1 dan AOA (sudut serang) 0º sehingga bentuk foil yang direkomendasikan untuk digunakan adalah sweep belakang.Kata kunci: hysucat, hambatan, gaya angkat, foil, CFDABSTRACTCatamaran hull-form using foil aims to produce better performance. Hydrofoil Supported-Catamaran (Hysucat) is a catamaran which is designed for high-speed craft using foil. This research was conducted with a numerical method approach to present fluid flow using RANS (Reynolds-Averaged Navier-Stokes). The numerical method uses two phases, namely water phase, and air phase to analyze catamaran hull-form, which have been modified being hysucat. Hysucat is distinguished by three types of foil form namely straight foil, backward sweep foil, and forward sweep foil with additional variations in chord line and angle of attack (AOA). The addition of foil in this study provides information that hysucat with backward foil, chord line 1.2, and AOA 0º reduce ship resistance by 21% from catamaran resistance without foil. The highest lift force is produced by hysucat with backward foil, chord line 1 and AOA 0º so that foil form which is recommended to be used is backward sweep foil.Keywords: hysucat, resistance, lift force, foil, CFD

scholarly journals Novel approach for adaptive coefficient tuning for the simulation of evaporating high-speed sprays injected into a high-temperature and high-pressure environment

2019 ◽  
Vol 21 (7) ◽  
pp. 1162-1179 ◽  
Author(s):  
DM Nsikane ◽  
K Vogiatzaki ◽  
RE Morgan ◽  
M Heikal ◽  
K Mustafa ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
High Speed ◽  
Injection Pressure ◽  
Coefficient Matrix ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Automated Simulation ◽  
Reynolds Averaged Navier Stokes

Producing reliable in-cylinder simulations for quick-turnaround engine development for industrial purposes is a challenging task for modern computational fluid dynamics, mostly because of the tuning effort required for the sub-models used in the various frameworks (the Reynolds-averaged Navier–Stokes and large eddy simulation). Tuning is required because of the need for modern engines to operate under a wider range of conditions and fuels. In this article, we suggest a novel methodology based on automated simulation parameter optimisation that is capable of delivering a priori a coefficient matrix for each operating condition. This approach produces excellent results for multiple comparison metrics like liquid and vapour penetration lengths, radial and axial mass fraction and temperature distributions. In this article, we also show for the first time that input model coefficients can potentially be linked to ambient boundary conditions in a physically consistent manner. Changes in injection pressure, charge pressure and charge density are considered. This paves the way for the tabulation of the constants in order to eliminate lengthy tuning iterations between operating conditions and move towards adaptive simulations as the piston moves changing the in-cylinder conditions. An additional discussion is performed for the validity range of existent models given that in recent years there has been a shift towards more extreme thermodynamic conditions in the injection stage (reaching the limits of transcritical flows). Although in this work the framework was implemented in the Reynolds-averaged Navier–Stokes context because this is the tool of preference of digital engineering currently by automotive industries, the approach can be easily extended in large eddy simulation.

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