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Abstract
An experimental investigation of the interaction between a double-orifice synthetic jet with an approaching turbulent boundary layer developing on the bottom wall of square channel has been carried out. Schlieren visualization and velocity measurement using hotwire anemometry are carried out to characterize the synthetic jet actuators arrangement. Detailed heat transfer measurements are carried out using liquid crystal thermography. Hotwire measurements on the wall surface have been reported to understand the interaction between the approaching boundary layer and synthetic jet. Maximum overall heat transfer enhancement of 55.48% at an actuation voltage of 55 V is observed with entropy generation number equal to 0.649. The amplitude modulation is observed to increase the heat transfer enhancement in comparison to that without amplitude modulation.
NOMENCLATURE
| D | = | orifice of synthetic jet actuator, m |
| fAM | = | modulation frequency, Hz |
| H | = | hue component of RGB |
| h | = | heat transfer coefficient, W/m2-K |
| k | = | thermal conductivity, W/m-K |
| L | = | length of heated section, m |
| Ns, a | = | augmentation entropy generation number |
| q′ | = | heat transfer rate per unit heated length, W/m |
| = | mass flow rate, kg/s | |
| t | = | time, s |
| T | = | temperature of the air, °C |
| Tb | = | bulk temperature of the mainstream, °C |
| T* | = | absolute bulk temperature of the mainstream, K |
| Ti | = | initial wall temperature, °C |
| = | entropy generation number | |
| Uavg | = | average velocity of flow, m/s |
| u | = | velocity in the x-direction, m/s |
| v | = | velocity in the y-direction, m/s |
| Vexc | = | actuator excitation voltage, V |
| x,y,z | = | streamwise (axial), transverse and spanwise coordinates, respectively |
Greek Symbols
| α | = | thermal diffusivity, m2/s |
| Δp/L | = | average frictional pressure gradient per unit heated length |
| ρ | = | density of the air, kg/m3 |
| τj | = | time step change based on Duhamel's theorem |
| τw | = | wall shear stress, N/m2 |
| ν | = | kinematic viscosity, m2/s |
Subscripts
| a | = | enhanced case (with excitation) |
| i | = | initial temperature |
| o | = | baseline case |
| Δp | = | pressure drop |
| ΔT | = | temperature difference |
| rms | = | root mean square component |
| w | = | wall condition |
Additional information
Notes on contributors
Adnan Qayoum
Adnan Qayoum is a professor in Mechanical Engineering at National Institute of Technology Srinagar. He received his M.E. degree in mechanical engineering from University of Roorkee and Ph.D. from Indian Institute of Technology Kanpur. His research interests are turbulent flow, flow control, flow visualization, and heat transfer enhancement. Currently he is working on heat transfer analysis of disk brakes.
Pradipta Kumar Panigrahi
Pradipta Kumar Panigrahi is a professor in Mechanical Engineering at Indian Institute of Technology Kanpur. At present he is Professor and Head of the Center for Lasers and Photonics at Indian Institute of Technology Kanpur. He did his Ph.D. and M.S. in Mechanical Engineering from Louisiana State University, Baton Rouge, LA. His research focuses on development of state-of-the-art experimental techniques preferably using lasers and detectors/sensors to analyze complex flow fields at both macro and micro scale. The other area of his interest is development of various flow control strategies with overall emphasis on improving the performance of various engineering devices and processes.