The following cold-flow study examines the interaction of the diffracted shock wave pattern and the resulting vortex loop emitted from a shock tube of various geometries, with an ejector having a round bell-shaped inlet. The focus of the study is to examine the performance of the ejector when using different jet geometries (primary flow) to entrain secondary flow through the ejector. These include two circular nozzles with internal diameters of 15mm and 30mm, two elliptical nozzles with minor to major axis ratios of a/b = 0.4 and 0.6 with b = 30mm, a square nozzle with side lengths of 30mm, and two exotic nozzles resembling a pair of lips with axis ratios of a/b = 0.2 and 0.5 with b = 30mm. Shock tube driver pressures of P 4 = 4, 8, and 12bar were studied, with the pressure of the shock tube driven section P 1 being atmospheric. High-speed schlieren photography using the Shimadzu Hypervision camera along with detailed pressure measurements along the ejector and the impulse created by the ejector were conducted. * Hossein. Zare-Behtash@glasgow.ac.uk

The present study involves the shock wave and consequent vortex loop generated when a shock tube with various nozzle geometries is employed. It aims to provide quantitative and qualitative insight into the physics of these compressible phenomena. The geometries included two elliptic nozzles with minor to major axis ratios of 0.4 and 0.6, a 15 mm circular nozzle and a 30 × 30 mm square nozzle. The experiments were performed for driver gas (air) pressures of 4, 8 and 12 bar.Schlieren, shadowgraphy, and PIV techniques were employed to visualise and quantify the induced flow field.

The focus of the current study is to examine experimentally the diffracted shock wave pattern and the consequent vortex loop formation, propagation, and decay from nozzles having singular corners.Non-intrusive qualitative and quantitative techniques: schlieren, shadowgraphy, and particle image velocimetry (PIV) are employed to analyse the induced flow fields. Eye-shaped nozzles were used with the corner joints representing singularities. The length of the minor axes are a = 6 and 15 mm, with the major axis b = 30 mm for both cases. The experiments are performed for flow Reynolds numbers in the range 0.8 ×10 5 and 4.6 ×10 5 . Air is used in both driver and driven sections of the shock tube.

Vortex loops are fundamental building blocks of supersonic free jets. Isolating them allows for an easier study and better understanding of such flows. The present study looks at the behaviour of compressible vortex loops of different shapes, generated due to the diffraction of a shock wave from a shock tube with different exit nozzle geometries. These include a 15mm diameter circular nozzle, two elliptical nozzles with minor to major axis ratios of 0.4 and 0.6, a 30 × 30mm square nozzle, and finally two exotic nozzles resembling a pair of lips with minor to major axis ratios of 0.2 and 0.5. The experiments were performed for diaphragm pressure ratios of P 4 /P 1 = 4, 8, and 12, with P 4 and P 1 being the pressures within the high pressure and low pressure compartments of the shock tube, respectively. High-speed schlieren photography as well as PIV measurements of both stream-wise and head-on flows have been conducted. * Hossein. Zare-Behtash@glasgow.ac.uk

Two in-house Pressure-Sensitive Paint (PSP) formulations have been developed and tested in the low-speed regime on the flow around a U-bend of strong curvature. The two PSP formulations use trisBathophenanthroline Ruthenium Perchlorate (Ru (II)) and Platinum tretakis (pentafluorophenyl) Porphyrin (PtTFPP) as their photoactive molecules, incorporated in identical sol-gel matrices. Ru (II) emits a broad peak centered at 610nm while PtTFPP emits a much narrower peak at 650nm. The paints were illuminated using two in-house constructed blue LED lights with peak emission of 468nm. These luminophores have been tested with gauge inlet pressures of 3000 and 1250 Pa respectively. A further sample was tested with a gauge pressure of 500 Pa. In-situ calibration was utilized to minimize the temperature dependency change between wind-on and wind-off images. Both paints captured the flow characteristics and gave predictable surface pressure maps despite the challenges inherent with using such low pressures. Keywords: PSP, low-speed, U-bend, internal flow INTRODUCTIONSeveral researchers have attempted to use pressuresensitive paints (PSP) at low speeds despite the inherent difficulties with such applications [1,2,3,4,5,6,7]. Of these researchers Bell [3] and Le Sant [7] managed extremely low errors (± 50 Pa). However, all of the applications of PSP to low-speed flow have been performed in large-scale wind tunnels. To this end it was decided to test the PSP formulations in use at the University of Manchester on a low-speed, internal flow.