https://nal-ir.nal.res.in/795/1/Pro_Aero_Sc_38_2002_elsevier.pdf

Aircraft viscous drag reduction using riblets

Engineering marvels found throughout living nature continually provide inspiration to researchers solving technical challenges. For example, skin from fast-swimming sharks intrigue researchers since its low-drag riblet microstructure is applicable to many low drag and self-cleaning (antifouling) applications. An overview of shark skin related studies that have been conducted in both open channel (external) and closed channel (internal) flow experiments is presented. Significant work has been conducted with the open channel flow, and less with closed channel flow. The results provide design guidance when developing novel low drag and self-cleaning surfaces for applications in the medical, marine, and industrial fields. Experimental parameters include riblet geometry, continuous and segmented configurations, fluid velocity (laminar and turbulent flow), fluid viscosity (water, oil, and air), closed channel height dimensions, wettability, and scalability. The results are discussed and conceptual models are shown suggesting the effect of viscosity, coatings, and the interaction between vortices and riblet surfaces.

Fluid Drag Reduction with Shark-Skin Riblet Inspired Microstructured Surfaces

Numerical models in simulating wire-plate electrostatic precipitators: A review

Fuel processing technology

Two-dimensional volume of fluid simulation studies on single bubble formation and dynamics in bubble columns

Flow simulation in an electrostatic precipitator of a thermal power plant

Influence of the inlet velocity profiles on the prediction of velocity distribution inside an electrostatic precipitator

Results of viscous drag reduction using 3M riblets on a swept wing with a general aviation wing (GAV)(2) airfoil section at low speeds are presented. The tests, made at a chord Reynolds number of 0.75 x 10 exp 6, covered an incidence range of 0-6 deg. Measurements consisted of surface-pressure distributions and total drag using wake survey over the range of incidence covered; in addition, mean velocity, streamwise turbulence intensity, and Reynolds shear-stress profiles in the boundary layer were measured just ahead of the trailing edge at zero incidence. Surface flow patterns on the wing were obtained using an oil-flow technique employing titanium dioxide as pigment. The results showed viscous drag reduction of about 8 percent at zero incidence, which decreased progressively to about 1 percent at an incidence of 6 deg. The fall in riblet effectiveness appears to be a result of significant riblet yaw angle effects observed at higher incidence. Some reduction in the turbulence intensity and Reynolds shear stress in the boundary layer on the wing's upper surface have been observed in the presence of riblets, as in two-dimensional flows.

Viscous Drag Reduction Using Riblets on a Swept Wing

THE study of turbulent drag reduction by use of riblets has been an area of significant research during the past de cade. Riblets with symmetric v grooves with adhesive-backed film manufactured the 3M Company (U.S.) have been widely used in earlier studies. The effectiveness of riblets in reducing the drag of a simple wo-dimensional configuration is fairly we 11 established now. Although there has been some effort to assess the effectiveness riblets on airfoils, the results reported by Sundaram et al on a NACA 0012 airfoils at low speeds have been particularly noteworthy.13; Their studies showed that both total and viscous drag reduction increased monotonically with an angle of attack up to 6 deg; it was also shown3 that the higher drag reduction resulted primarily from airfoil upper (or suction) surface, suggesting increased effectiveness of riblets in adverse pressure gradients. In a subsequent study Subaschandar et al., who extending the work of Sundaram etal to higher angles of attack (by using the same NACA 0012 model13; and the same wind tunnel), it was observed that the drag reduction decreased rapidly beyond a = 6 deg with virtually no drag reduction a =12 deg. The present study is an attempt to assess the total drag reduction that is due to riblets on a cambered airfoil up to high angles of attack low speeds. The 13% thickness General Aviation Wing [GAW(2)]13;

/pdf/drag-reduction-due-to-riblets-on-a-gaw-2-airfoil-2nu438nldp.pdf

Drag Reduction Due to Riblets on a GAW(2) Airfoil

This paper presents a Computational Fluid Dynamics (CFD) model for a wire-plate electrostatic precipitator (ESP). The turbulent gas flow and the particle motion under electrostatic forces are modelled using the CFD code FLUENT. Numerical calculations for the gas flow are carried out by solving the Reynolds-averaged Navier-Stokes equations and turbulence is modelled using the k-e turbulence model. An additional source term is added to the gas flow equation to capture the effect of electric field. This additional source term is obtained by solving a coupled system of the electric field and charge transport equations. The particle phase is simulated by using Discrete Phase Model (DPM). The results of the simulation are presented showing the particle trajectory inside the ESP under the influence of both aerodynamic and electrostatic forces. The simulated results have been validated by the established data. The model developed is useful to gain insight into the particle collection phenomena that takes place inside an industrial ESP.

https://espace.library.uq.edu.au/view/UQ:121268/Haque_afmc_16_07.pdf

N. Subaschandar

Papers

Flow simulation in an electrostatic precipitator of a thermal power plant

Influence of the inlet velocity profiles on the prediction of velocity distribution inside an electrostatic precipitator

Viscous Drag Reduction Using Riblets on a Swept Wing

Drag Reduction Due to Riblets on a GAW(2) Airfoil

A Numerical Model of an Electrostatic Precipitator