Influences of RVG Positions on the Periodic Flow Profiles

Abstract

The effects on the positions of rib vortex generators (RVGs) for periodic laminar flow behavior are presented numerically in three-dimensional. The RVGs with constant blockage ratio (b/H, BR = 0.15), the pitch ratio (P/H, PR = 1), and flow attack angle (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mi>α</mml:mi><mml:mo>=</mml:mo><mml:msup><mml:mrow><mml:mn>30</mml:mn></mml:mrow><mml:mrow><mml:mo>°</mml:mo></mml:mrow></mml:msup></mml:math>) are inserted in isothermal walls of the square channel. The SIMPLE algorithm and the finite volume method (FVM) are applied for the computational domain. The influences of different gap ratios (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mi>g</mml:mi><mml:mo>/</mml:mo><mml:mi>H</mml:mi></mml:math>= 0–0.35) for Reynolds number based on the hydraulic diameter (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mrow><mml:msub><mml:mrow><mml:mi>D</mml:mi></mml:mrow><mml:mrow><mml:mi>h</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>), Re = 100–1200, are investigated. It is found that the flow profiles can be divided into two parts; the first, similar in flow configuration, but different in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M4"><mml:mi>u</mml:mi><mml:mo>/</mml:mo><mml:msub><mml:mrow><mml:mi>u</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msub></mml:math>values, is called “periodic flow” and the second, similar in both flow configuration and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M5"><mml:mi>u</mml:mi><mml:mo>/</mml:mo><mml:msub><mml:mrow><mml:mi>u</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msub></mml:math>values, is called “fully developed periodic flow.” The results reveal that the periodic flow profiles appear around 2nd-3rd modules while the fully developed flow profiles occur around 6th–9th modules. In addition, the periodic flow profiles and fully developed periodic flow profiles become faster in case of the lowest continuous flow area (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M6"><mml:mi>g</mml:mi><mml:mo>/</mml:mo><mml:mi>H</mml:mi></mml:math>= 0.20, 0.25, and 0.30) and the regimes close to the RVG.