To improve the performance of particle image velocimetry in measuring instantaneous velocity fields, direct cross-correlation of image fields can be used in place of auto-correlation methods of interrogation of double- or multiple-exposure recordings. With improved speed of photographic recording and increased resolution of video array detectors, cross-correlation methods of interrogation of successive single-exposure frames can be used to measure the separation of pairs of particle images between successive frames. By knowing the extent of image shifting used in a multiple-exposure and by a priori knowledge of the mean flow-field, the cross-correlation of different sized interrogation spots with known separation can be optimized in terms of spatial resolution, detection rate, accuracy and reliability.

Theory of cross-correlation analysis of PIV images : Image analysis as measuring technique in flows

The efficiency and mechanisms of cooling a constant heat flux surface by impinging synthetic jets were investigated experimentally and compared to cooling with continuous jets. Effects of jet formation frequency and Reynolds number at different nozzle-to-surface distances (H/d) were investigated. High formation frequency (f=1200 Hz) synthetic jets were found to remove heat better than low frequency (f=420 Hz) jets for small H/d, while low frequency jets are more effective at larger Hid. Moreover, synthetic jets are about three times more effective in cooling than continuous jets at the same Reynolds number. Using particle image velocimetry, it was shown that the higher formation frequency jets are associated with breakdown and merging of vortices before they impinge on the surface. For the lower frequency jets, the wavelength between coherent structures is larger such that vortex rings impinge on the surface separately.

Electronic Cooling Using Synthetic Jet Impingement

The relationship between the upstream boundary layer and the low-frequency, large-scale unsteadiness of the separated flow in a Mach 2 compression ramp interaction is investigated by performing wide-field particle image velocimetry (PIV) and planar laser scattering (PLS) measurements in streamwise–spanwise planes. Planar laser scattering measurements in the upstream boundary layer indicate the presence of spanwise strips of elongated regions of uniform momentum with lengths greater than 40?. These long coherent structures have been observed in a Mach 2 supersonic boundary layer (Ganapathisubramani, Clemens & Dolling 2006) and they exhibit strong similarities to those that have been found in incompressible boundary layers (Tomkins & Adrian 2003; Ganapathisubramani, Longmire & Marusic 2003). At a wall-normal location of y/?=0.2, the inferred instantaneous separation line of the separation region is found to oscillate between x/?=?3 and ?1 (where x/?=0 is the ramp corner). The instantaneous spanwise separation line is found to respond to the elongated regions of uniform momentum. It is shown that high- and low-momentum regions are correlated with smaller and larger size of the separation region, respectively. Furthermore, the instantaneous separation line exhibits large-scale undulations that conform to the low- and high-speed regions in the upstream boundary layer. The low-frequency unsteadiness of the separation region/shock foot observed in numerous previous studies can be explained by a turbulent mechanism that includes these elongated regions of uniform momentum

Effects of upstream boundary layer on the unsteadiness of shock induced separation

Thank you very much for reading atmospheric boundary layer flows their structure and measurement. As you may know, people have search numerous times for their chosen books like this atmospheric boundary layer flows their structure and measurement, but end up in malicious downloads. Rather than enjoying a good book with a cup of coffee in the afternoon, instead they are facing with some malicious virus inside their laptop.

Atmospheric Boundary Layer Flows Their Structure And Measurement

The Physical Chemistry of Electrolytic Solutions.

The work presented in this paper is carried out under the Skycanner project with the aim to study a fleet of coordinated mini-drones that will adaptively sample cumulus-type clouds, over periods of the order of one hour.

https://hal-enac.archives-ouvertes.fr/hal-01353936/document

Optimal design of long endurance mini UAVs for atmospheric measurement

Thermal management system models for overall aircraft design

An extension to work by NACA was presented for a square flap opening from a large cavity to a transonic turbulent boundary layer. For flap angles from 18 to 45 deg, the discharge coefficients decrease at given stagnation pressure ratio between the cavity and the freestream. This loss of performance is likely linked to competitive flow features. At a given flap deflection and Mach number, dimensionless discharge increases nearly linearly with pressure ratio.

/pdf/review-and-experimental-survey-of-flapped-exhaust-1got52xq07.pdf

Review and Experimental Survey of Flapped Exhaust Performance

Using CFD analyses, the effects of flow control techniques, as the contour bump and the surface cooling concepts, are separately investigated in transonic periodic flow over 14% and 18% biconvex aerofoils. For these aerofoils both cooling and bump contour, which was located in the vicinity of the mean shock position on the lower surface of the aerofoil, have a positive influence on drag reduction and buffeting alleviation. The Tijdeman’s Type A, B and C shock oscillations are well identified on the

Drag reduction and buffeting alleviation in transonic periodic flow over biconvex airfoils

Major customer requirements and design drivers in aerospace are highlighted. Some of the current research activities at Queens University Belfast in meeting the customer requirements are presented. Key cost drivers were identified and a cost model was developed and validated. The cost model was used to develop methodologies for evaluation of the cost benefits of Design for Manufacturing and Assembly, including trade -off studies between Aerodynamics, Manufacturing and Assembly for allocation of optimum tolerance s for minimum cost. The results were extrapolated to a whole aircraft to estimate savings in Direct Operating Cost. The study showed (for Airbus 320 class aircraft) that with an approach towards Design for Manufacturing and Assembly, and focusing on the allocation of optimum tolerances, one percent reduction in aircraft cost and correspondingly half of one percent reduction in Direct Operating Cost could be achieved. The work led to the setting up of a Center of Excellence on Integrated Aircraft Technol ogies at Queens University Belfast, brief details of which are also given in the paper.

Emmanuel Benard

Papers

Optimal design of long endurance mini UAVs for atmospheric measurement

Thermal management system models for overall aircraft design

Review and Experimental Survey of Flapped Exhaust Performance

Drag reduction and buffeting alleviation in transonic periodic flow over biconvex airfoils

Research into integrated aircraft technologies