Measuring Vortex-Induced Vibration with Hot Wire in Wind Tunnel
Long cantilever stings that support aerodynamic models in wind tunnels are a potential source of vibration problems which would damage test data quality, many documents use the methods of setting acceleration sensors on model to measure vibration of model-sting system, but setting sensors on little scale model is hard to realize, and sensors could interfere with flow field around the model. For purpose of reducing flow field interference, a method of hot wire probe measuring wake to acquire vibration parameters of model is tried, this way is easy to realize for little scale model. At the same time, methods of accelerator signal frequency domain filtering and frequency domain integration are used to acquire vibration model parameters of model-sting for comparison with data of hot wire, this method could improve the SNR of effective signal. Using method of accelerator signal power spectrum analysis, three order vibration frequencies of 31.1Hz¡¢120.9 Hz and 221.4Hz of the system are acquired. Using method of frequency domain filtering and frequency domain integration, the vibration mode and node of the system are acquired. Using method of hot wire measuring wake, vortex shedding frequencies of 31.1Hz and 124.1 Hz, and the model buffet boundary are acquired. Experiment results show that, the method of hot wire measuring model wake vortex shedding frequency for analysis of aircraft model vibration, is convenient for little scale model test, is a practical method for vortex-induced vibration measurement.
Investigation on the interference of rear sting supports at high angle of attack in low speed wind-tunnel
The high alpha aerodynamic of low speed wind tunnel experiments are necessary for the future advanced aircrafts,and the most of aircrafts models are supported by rear sting,but the interference of sting are not deducted from the test results before,in order to research the interference of the sting,this study was conducted in CARDC and the results can be referenced to the other aircrafts models for low speed wind tunnel test.The investigation of interference on the rear sting supports system was carried out in the 3.2m wind tunnel of CARDC,the airplane model was supported with the extension system and the rear rigs was fixed on the end of balance,then,the interference of rear rig could be gotten.The quantity of the interference of the rear rigs and its rules varying with the α and the β are presented in this paper,at the same time,the influence of various configuration of rear rigs on the interference rules have been analyzed.Some sugguestions for the rear rig design are brought forward in the paper too.
Immunization with Brucella melitensis Rev 1 against Brucella ovis infection of rams.
The efficacy of Brucella Melitensis Rev 1 vaccine (Rev 1) for the prophylaxis of Brucella ovis ram epididymitis was evaluated. Twenty-nine 3-month-old rams were vaccinated with 2 X 10(9) Rev 1 and 14 were revaccinated with 5 X 10(8) at 14 months of age. Six rams remained unvaccinated as a control group. All rams were challenged with 5 X 10(8) B. ovis at 21 months of age. Before being slaughtered 8 weeks later, only one vaccinated ram developed epididymitis while four of the six control rams developed testicular alterations. Genital and selected extragenital organs and lymph nodes were removed at slaughter and inoculated on selective media. B. ovis was isolated from 26.6% of the vaccinated rams, 21.4% of the revaccinated rams and 100% of control rams. Portions of epididymis, testes and vesicular glands were also used for pathological studies. More severe lesions were observed in control rams than in vaccinated ones. In conclusion, these results show that vaccination of young lambs, followed or not by revaccination, is a suitable method for the prophylaxis of B. ovis infection of rams.