No description available.

The thesis aims to provide an evaluation on the Volvo 1/5th scaled wind tunnel regarding its potentials and capabilities in aerodynamic study. The flow quality in the test section was evaluated. The experiments were performed included measurements of airspeed stability, tunnel-wall boundary layer profile and horizontal buoyancy. A numerical model was developed to predict the boundary layer thickness on the test floor. Repeatability tests were also conducted to establish the appropriate operating regime.A correlation study between the 1/5th scaled wind tunnel (MWT) and full scale wind tunnel (PVT) was performed using steady force and unsteady pressure measurements. The Volvo Aero 2020 concept car was selected to be the test model.The Reynolds effect and the tunnel-wall boundary layer interference were identified in the steady force measurements. Unsteady near-wake phenomena such as wake pumping and wake flapping were discussed in the unsteady base pressure measurements.

An aeroacoustic study was conducted on a 26%-scale Boeing 777 main landing gear in the Virginia Tech (VT) Anechoic Stability Wind Tunnel. The VT Anechoic Stability Wind Tunnel allowed noise measurements to be carried out using both a 63-elements microphone phased array and a linear array of 15 microphones. The noise sources were identified from the flyover view under various flow speeds and the phased array positioned in both the near and far-field. The directivity pattern of the landing gear was determined using the linear array of microphones. The effectiveness of 4 passive noise control devices was evaluated. The 26%-scale model tested was a faithful reproduction of the full-scale landing gear and included most of the full-scale details with accuracy down to 3 mm. The same landing gear model was previously tested in the original hard-walled configuration of the VT tunnel with the same phased array mounted on the wall of the test section, i.e. near-field position. Thus, the new anechoic configuration of the VT wind tunnel offered a unique opportunity to directly compare, using the same gear model and phased array instrumentation, data collected in hard-walled and semi-anechoic test sections. The main objectives of the present work were (i) to evaluate the validity of conducting aeroacoustic studies in non-acoustically treated, hard-walled wind tunnels, (ii) to test the effectiveness of various streamlining devices (passive noise control) at different flyover locations, and (iii) to assess if phased array measurements can be used to estimate noise reduction. As expected, the results from this work show that a reduction of the background noise (e.g. anechoic configuration) leads to significantly cleaner beamforming maps and allows one to locate noise sources that would not be identified otherwise. By using the integrated spectra for the baseline landing gear, it was found that in the hard-walled test section the levels of the landing gear noise were overestimated. Phased array measurements in the near and far-field positions were also compared in the anechoic configuration. The results showed that straight under the gear, near-field measurements located only the lower-truck noise sources, i.e. noise components located behind the truck were shielded. It was thus demonstrated that near-field, phased-array measurements of the landing gear noise straight under the gear are not suitable. The array was also placed in the far-field, on the rear-arc of the landing gear. From this position, other noise sources such as the strut could be identified. This result demonstrated that noise from the landing gear on the flyover path cannot be characterized by only taking phased array measurement right under the gear. The noise reduction potential of various streamlining devices was estimated from phased array measurements (by integrating the beamforming maps) and using the linear array of individually calibrated microphones. Comparison of the two approaches showed that the reductions estimated from the phased array and a single microphone were in good agreement in the far-field. However, it was found that in the near-field, straight under the gear, phased array measurements greatly overestimate the attenuation. / Master of Science

<p>The first force and moment measurements were conducted in the BAM6QT. Three 7-degree half-angle sharp cones were tested, one with base radius of 4.5 in. and two with base radius of 3.5 in. made out of different materials. Models were tested at 0 and 2 degrees angle of attack. Models were tested over a range of burst pressures and Reynolds numbers. Models were fitted onto a strain gauge, 6 component, internal, moment balance. Multiple assemblies were tested that mounted the balance in the BAM6QT. High-speed schlieren video was used to monitor flow conditions and track the movement of the tunnel and model. Three entries were performed in the BAM6QT. The improvement in data quality with each new entry is shown and the startup and running loads from entry 3 are analyzed.</p> <p>Startup loads were measured and are of importance in determining the load range needed to operate in the BAM6QT. Large startup loads up to 40X the running load were identified. Tunnel movement was measured and was used to approximate the inertial loading during startup and the run. The inertial loading was not found to be the cause of the large startup loads. Schlieren video was used to qualitatively review the startup flow. It was found the large startup loads in axial force were plausibly from the high-pressure subsonic flow evacuating the nozzle. For normal force and pitching moment, the startup loads peak at a different time than axial force and appear to be from a shock-shock interaction nearby the model. Trends in startup load with changing model geometry, AoA, and burst pressure were put together to form an empirical estimation for startup loads sharp cones. </p> <p>Running loads were profiled and found to be trending with burst pressure and model geometry similarly to Newtonian flow theory predictions. However, due to the lack of a base pressure measurement, the results are uncorrected for sting effects and differ from Newtonian flow theory by a scalar. A 5.3 Hz oscillation in axial force was identified. The frequency of the oscillation is the same as the frequency of the quasi-steady flow periods caused by the reflection of the expansion fan in the driver tube. Normal force during the running load was found to be measuring positive loads when at 0 degrees angle of attack. Both the axial and normal force phenomena were unexpected and were investigated but both require further research. </p> <p><br></p> <p><br></p> <p><br></p> <p><br></p>

Baigiamajame magistro darbe aptariama oro srauto greičio netolygumo aerodinaminiame vamzdyje problema ir aktualumas. Išanalizuota būdinga mokslinė literatūra ir aprašyti būdingiausi oro srauto greičio darbinės dalies skerspjūvyje nustatymo metodai. Naudojant CAD aplinkos programą sumodeliuotas trimatis aerodinaminio vamzdžio modelis ir pritaikius analizės baigtiniais elementais metodą, atliktas oro srauto greičio pasiskirstymo aerodinaminio vamzdžio darbinėje dalyje ir jos viduriniame skespjūvyje tyrimas. Tyrimo rezultatai išanalizuoti ir pateiktos išvados ir siūlymai. / In this master's thesis deals discusses the inadequacy of air flow speed in wind tunnel and the relevance of the problem. Performed analysis of the scientific literature and describe the most typical technique of air flow mesurements in wind tunnel. Using a CAD program modeled three-dimensional wind tunnel model and performed air flow velocity testing in wind tunenel test section and their midle cros area section usig CFD program. The results is evaluated and stated the conclusions and suggestions.

An approach for designing a high-enthalpy wind tunnel driven by exothermic chemical reactions was developed. Nozzle contours were designed using CONTUR, a program implementing the method of characteristics, to design nozzle contours at various flow conditions. A reacting mixture including nitrous oxide has been identified as the best candidate for providing clean air at high temperatures. The nitrous oxide has a few performance factors that were considered, specifically the combustion of the gas. Initial CFD simulations were performed on the nozzle and test region to validate flow characteristics and possible issues. Initial results show a fairly uniform exit velocity and ability to perform testing. In a second phase of the work, two generic, high-speed missile configurations were explored using numerical simulation. The mean flow was computed on both geometries at 0 and 45 roll and 0, 1, and 10 angle of attack. The computations identified complex flow structures, including three-dimensional shock/boundary-layer interactions, that varied considerably with angle of attack.

Pracovní podmínky atomizérů v reálných operacích v průmyslu a zemědělství se liší od podmínek laboratorních, ve kterých jsou atomizéry testovány. Částečné přiblížení k realističtějším podmínkám nám může poskytnout použití větrného tunelu. Větrný tunel se používá k simulaci okolního proudění. Studium spreje ve větrném tunelu nám poskytne realističtější představu o chování spreje. Tato diplomová práce se zabývá návrhem malého, nízko rychlostního větrného tunelu pro experimenty s tlakovými vířivými tryskami s obtokem v příčném a podélném proudění. Existuje mnoho typů větrných tunelů, ale jako nejvhodnější typ byl zvolen otevřený, výtlačný větrný tunel s uzavřenou testovací sekcí. Výhodou jsou jeho kompaktní rozměry, ochrana částí tunelu před kapičkami spreje a poměrně jednoduchý návrh. Konstrukce větrného tunelu se skládá z několika částí, každá část je zkonstruována tak, aby bylo dosaženo co nejlepší kvality proudu v testovací sekci. Sprej je zkoumán pomocí optických metod Fázové Dopplerovské anemometrie (PDA), Laserové Dopplerovské anemometrie (LDA), Integrální laserová anemometrie (PIV) a pomocí vysokorychlostního záznamu. Tyto optické metody kladou speciální požadavky na konstrukci tunelu, především na konstrukci testovací sekce, která musí umožňovat optický přístup ke spreji a musí být pro tyto měřící techniky uzpůsobena. Rychlost v testovací sekci se pohybuje v rozmezí 0 až 40 m/s s intenzitou turbulence pod 0,7 %. V závěru práce je ukázka vizualizace spreje, v příčném proudění, pomocí vysokorychlostní kamery. Okolní proudění mění rozpadovou vzdálenost spreje, úhel kužele spreje i jeho tvar. Dochází k vymývání menších kapek, které jsou unášeny okolním proudem.

An approach for designing a high-enthalpy wind tunnel driven by exothermic chemical reactions was developed. Nozzle contours were designed using CONTUR, a program implementing the method of characteristics, to design nozzle contours at various flow conditions. A reacting mixture including nitrous oxide has been identified as the best candidate for providing clean air at high temperatures. The nitrous oxide has a few performance factors that were considered, specifically the combustion of the gas. Initial CFD simulations were performed on the nozzle and test region to validate flow characteristics and possible issues. Initial results show a fairly uniform exit velocity and ability to perform testing. In a second phase of the work, two generic, high-speed missile configurations were explored using numerical simulation. The mean flow was computed on both geometries at 0 and 45 roll and 0, 1, and 10 angle of attack. The computations identified complex flow structures, including three-dimensional shock/boundary-layer interactions, that varied considerably with angle of attack. <br>

No description available.

The efficient study of liquid droplets ranging from micrometers to a few centimeters by levitation is usually hindered by conventional design limitations. This is due to continuous droplet deformation in the test section. This research discusses the development of a robust design methodology for large droplet-stabilization (d > Capillary Number (Ca)) vertical wind tunnels. A modeling and simulation design environment has been developed that involves component sizing and integration at a central ANSYS-Fluent platform, followed by design optimization. The work inculcates numerical analysis of guide vanes to minimize the viscous losses and, subsequently, the wind tunnel dimensions. The process is followed by the design of honeycomb and wire screens and their analyses for a given geometry. A multi-variable design optimization problem has been optimized with response surface approximations. Statistical modeling of the expensive functions obtained from the solution of Navier-stokes equations has been accomplished in order to deal with non-linear and discontinuous behavior. Numerical optimization of the meta-model can help to find the most feasible wind tunnel design with computational efficiency. A non-conventional design with varying test area cross-sections has been introduced to investigate the droplet stability in constantly changing velocity profiles. Longitudinal as well as lateral velocity variations in the test section, creating velocity buckets with minimum turbulence intensity, has been introduced and analyzed using novel concept designs. The research highlights a systematic design methodology and an alternate configuration for liquid droplet wind tunnels while focusing on stable droplet levitation.