KARAKTERISTIK ALIRAN DI SEKITAR SILINDER SIRKULAR DAN SILINDER BERSIRIP

Aliran yang melalui suatu benda akan menghasilkan karakeristik aliran yang sangat tergantung pada beberapa parameter fisik, diantaranya; bentuk benda, kondisi permukaan, maupun orientasi benda yang dilintasi. Penelitian ini, penulis menggunakan software Gambit 2.4 dan Fluent 6.3 untuk memodelkan silinder bersirip dengan variasi jarak antar fin. Diameter silinder, panjang silinder, panjang fin, dan tebal fin adalah variabel yang tetap konstan. Variabel yang diubah adalah jarak antar fin, yaitu 10 mm, 14 mm, dan 18 mm. Simulasi numerik pada penelitian ini dilakukan dengan pendekatan 3D-steady flow Reynolds Averaged-Navier Stokes (RANS) dan RNG k-ε. Properties udara yang digunakan pada kondisi STP dengan temperatur 28oC adalah, densitas (ρ) = 1,17 kg/m3 dan viskositas (μ)=1,85 x 10-5 N.s/m2. Kondisi inlet aliran udara, velocity inlet 16 m/s dan intensitas turbulensi 1,56 % diterapkan pada kondisi batas inlet domain simulasi numerik. Aliran fluida yang melalui silinder yang terdapat clearance antara silinder dan dinding tidak terbentuk pasangan vorteks dengan arah aliran tertutup (close loop) sebagaimana umumnya vorteks aliran 2D di belakang sililnder sirkular. Terbentuk vorteks pada celah antar fin terutama pada celah antar fin di dekat clearance antara silinder bersirip dan dinding. Semakin banyak vorteks yang terbentuk, maka akan menghasilkan induced drag yang besar terutama pada silinder bersirip dengan jarak antar fin yang lebih sempit. Silinder bersirip menghasilkan daerah wake yang lebih panjang sebelum terjadi attached flow.

Download Full-text

Multi-stage nozzle-shape optimization for pulsed hydrogen–air detonation combustor

Advances in Mechanical Engineering ◽

10.1177/1687814017690955 ◽

2017 ◽

Vol 9 (2) ◽

pp. 168781401769095 ◽

Cited By ~ 4

Author(s):

Francesco Ornano ◽

James Braun ◽

Bayindir Huseyin Saracoglu ◽

Guillermo Paniagua

Keyword(s):

Steady Flow ◽

Combustion Process ◽

Differential Evolution Algorithm ◽

Three Dimensions ◽

Sudden Expansion ◽

Navier Stokes ◽

Optimization Strategy ◽

Detonation Products ◽

Multi Stage ◽

Reynolds Averaged Navier Stokes

Thermal engines based on pressure gain combustion offer new opportunities to generate thrust with enhanced efficiency and relatively simple machinery. The sudden expansion of detonation products from a single-opening tube yields thrust, although this is suboptimal. In this article, we present the complete design optimization strategy for nozzles exposed to detonation pulses, combining unsteady Reynolds-averaged Navier–Stokes solvers with the accurate modeling of the combustion process. The parameterized shape of the nozzle is optimized using a differential evolution algorithm to maximize the force at the nozzle exhaust. The design of experiments begins with a first optimization considering steady-flow conditions, subsequently followed by a refined optimization for transient supersonic flow pulse. Finally, the optimized nozzle performance is assessed in three dimensions with unsteady Reynolds-averaged Navier–Stokes capturing the deflagration-to-detonation transition of a stoichiometric, premixed hydrogen–air mixture. The optimized nozzle can deliver 80% more thrust than a standard detonation tube and about 2% more than the optimized results assuming steady-flow operation. This study proposes a new multi-fidelity approach to optimize the design of nozzles exposed to transient operation, instead of the traditional methods proposed for steady-flow operation.

Download Full-text

Manufactured solutions for steady-flow Reynolds-averaged Navier–Stokes solvers

International Journal of Computational Fluid Dynamics ◽

10.1080/10618562.2012.717617 ◽

2012 ◽

Vol 26 (5) ◽

pp. 313-332 ◽

Cited By ~ 11

Author(s):

L. Eça ◽

M. Hoekstra ◽

G. Vaz

Keyword(s):

Steady Flow ◽

Navier Stokes ◽

Manufactured Solutions ◽

Reynolds Averaged Navier Stokes

Download Full-text

Scalar mixing in a Kelvin-Helmholtz shear layer and implications for Reynolds-averaged Navier-Stokes modeling of mixing layers

Physical Review E ◽

10.1103/physreve.103.053108 ◽

2021 ◽

Vol 103 (5) ◽

Author(s):

Brandon E. Morgan

Keyword(s):

Shear Layer ◽

Mixing Layers ◽

Navier Stokes ◽

Scalar Mixing ◽

Reynolds Averaged Navier Stokes

Download Full-text

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

Proceedings of the Institution of Mechanical Engineers Part M Journal of Engineering for the Maritime Environment ◽

10.1177/1475090216642468 ◽

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.

Download Full-text