The boundary layer equations for plane, incompressible, and steady flow are 

$$\matrix{ {u{{\partial u} \over {\partial x}} + v{{\partial u} \over {\partial y}} = - {1 \over \varrho }{{\partial p} \over {\partial x}} + v{{{\partial ^2}u} \over {\partial {y^2}}},} \cr {0 = {{\partial p} \over {\partial y}},} \cr {{{\partial u} \over {\partial x}} + {{\partial v} \over {\partial y}} = 0.} \cr }$$

Boundary Layer Theory

Life in Moving Fluids—The physical biology of flow

Synthesis Of Subsonic Airplane Design

A NiO@rGO nanocomposite is prepared by a freeze-drying method combined with heat treatment. The morphology and structure are analyzed through X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectra, and X-ray photoelectron spectroscopy. The results clearly show that NiO nanoparticles are uniformly anchored on the surface of the rGO nanosheet. The gas-sensing performance of the nanocomposite is also investigated to detect hydrogen. The NiO@rGO sensor exhibits good gas-sensing performance with high sensitivity, fast response, good reversibility, and selectivity toward hydrogen. The relative response of the sensor to 1% hydrogen is 0.64, the response time is 28 s, and the recovery time is 142 s. The improved sensing performance is due to the effective electron transfer between the NiO nanoparticles and rGO nanosheet.

Effective hydrogen gas sensor based on NiO@rGO nanocomposite

Vertebrate Flight Mechanics Physiology Morphology Ecology And Evolution

Passive drag reduction of square back road vehicles

An investigation is presented of the response of a three-degree-of-freedom system with quadratic nonlinearities and the autoparametric resonances ω3≈2ω2 and ω2≈2ω1 to a harmonic excitation of the third mode, where the ω
 m
 are the linear natural frequencies of the system. The method of multiple scales is used to determine six first-order nonlinear ordinary differential equations that govern the time variation of the amplitudes and phases of the interacting modes. The fixed points of these equations are obtained and their stability is determined. For certain parameter values, the fixed points are found to lose stability due to Hopf bifurcations and consequently the system exhibits amplitude-and phase-modulated motions. Regions where the amplitudes and phases display periodic, quasiperiodic, and chaotic time variations and hence regions where the overall system motion is periodically, quasiperiodically, and chaotically modulated are determined. Using various numerical simulations, we investigated nonperiodic solutions of the modulation equations using the amplitudeF of the excitation as a control parameter. As the excitation amplitudeF is increased, the fixed points of the modulation equations exhibit an instability due to a Hopf bifurcation, leading to limit-cycle solutions of the modulation equations. AsF is increased further, the limit cycle undergoes a period-doubling bifurcation followed by a secondary Hopf bifurcation, resulting in either a two-period quasiperiodic or a phase-locked solution. AsF is increased further, there is a torus breakdown and the solution of the modulation equations becomes chaotic, resulting in a chaotically modulated motion of the system.

Three-mode interactions in harmonically excited systems with quadratic nonlinearities

The aerodynamic parameters of a preliminary winged-hull airship design are investigated. The research methodology involved the use of numerical simulation and wind tunnel testing. The aerodynamic parameters of the design are first computed using a commercial CFD code. The force and moment coefficients are then measured on a scaled model in the IIUM low speed wind tunnel. The experimental results generally agree with the CFD predicted data. Addition of a wing to conventional airship increases the lift substantially with a reasonable increase in drag. The longitudinal and directional stabilities were found to be statically stable, however, both the conventional airship and the hybrid airship were found to have poor rolling stability. CFD simulations show that modifications to the wing placement and its dihedral have strong positive effect on the rolling stability.

Investigation of Aerodynamic Parameters of a Hybrid Airship

Experimental study on the mean flow characteristics of a supersonic multiple jet configuration

Birds are known for their agility, manoeuvrability, and flexibility during flight. These features allow their ability to fly under a large range of flight conditions. Bio flyers and bio aerodynamic/fluid surfaces have inspired many to perform experiments and simulations as well as to relate their results to engineering applications. Wings specifically have been the most inspirational element. Aerodynamic forces, structure, unsteady flow, fluid-structure interaction, flow control, flow adaptive elements and mechanisms, flow vortices, flapping mechanisms, and hovering flight of birds are examples of research interests. This paper presents an overview of prior analyses and experiments on the aerodynamic performance and mechanical properties of birds in steady non-flapping flight.

/pdf/a-review-on-aerodynamics-of-non-flapping-bird-wings-19882uhwqr.pdf

Waqar Asrar

Papers

Passive drag reduction of square back road vehicles

Three-mode interactions in harmonically excited systems with quadratic nonlinearities

Investigation of Aerodynamic Parameters of a Hybrid Airship

Experimental study on the mean flow characteristics of a supersonic multiple jet configuration

A Review on Aerodynamics of Non-Flapping Bird Wings