Aeroelastic testing of LCA wing models - Model fabrication - Ground testing - Wind tunnel testing and Data analysis

Aeroelastic Testing Programme of Scaled Aeroelastic model of LCA half wing with rigid fuselage

Arthralgia in South Indian patients with pulmonary tuberculosis during treatment with pyrazinamide and rifampicin

Arthralgia was the major adverse reaction encountered in a clinical trial of the treatment of pulmonary tuberculosis with three short-course regimens containing pyrazinamide in South Indian patients. The first regimen was of rifampicin, streptomycin, isoniazid and pyrazinamide given daily for three months; the second was of the same four drugs daily for three months followed by streptomycin, isoniazid and pyrazinamide twice-weekly for two months, and the third was the same as the second except that rifampicin was not administered. Arthralgia was reported in 36% of 353 rifampicin patients and 66% of 179 non-rifampicin patients, a highly significant difference (p<0.001). The onset of arthralgia was mostly during the first two months of chemotherapy. The knees were affected in about 90% followed by the ankles in about 50% of the patients with arthralgia, and about 60% of these patients had one or more of the signs, swelling, tenderness and limitation of joint movement. Chemotherapy was modified in 10 rifampicin and 15 non-rifampicin patients; the rest of the patients were managed with symptomatic treatment with analgesics. There was a two to three fold increase in serum uric acid concentrations by the end of the first month and the concentrations were more or less stationary throughout the rest of the daily phase of treatment. The mean concentration during the daily phase of treatment in patients with arthralgia (0.482 mmoles/litre) was similar to that in those without arthralgia (0.484 mmoles/litre), while that in the rifampicin patients (0.476 mmoles/litre) was significantly lower (p=0.03) than that in the non-rifampicin patients (0.495 mmoles/litre)

Experimental Study on gsLVM3 for Transonic Buffet Estimation

In modern launch vehicles, the unsteady aerodynamic forces caused by flow separation during the transonic regime induce aeroelastic instabilities like buffeting, which may lead to structural failure. Quantifying the buffet loads in the critical transonic regime is important to ensure the safety of the vehicle structure. The complexity of the buffeting phenomena makes the computational effort ifficult to predict the aerodynamic-elastic-inertial interactions. Hence the designer has to employ experimental approach to evaluate the necessary aeroelastic characteristics of launch vehicles. This paper presents a case study of experimental aeroelastic studies on gsLVM3 launch vehicle. For this an aerodynamically shaped and dynamically scaled model is designed, fabricated and wind tunnel tested. The responses of the mounted sensors on the model have been acquired during the tunnel testing and analyzed. The transonic buffet experienced by the model has been presented in the form of dynamic bending moment for different flight conditions. Finally, the critical buffet loads for the full scale vehicle are obtained using appropriate scale factor

Aeroelastic testing of aerospace vehicles - Experiences gained during four decades

Aerospace vehicles are constructed as light weight, thin walled structures, in order to facilitate more pay loads with improved flight performance. Further, the complex aerodynamic shape requirements bring additional problems to structural designers and analysts to qualiy the thin-walled structures; for example wings, fails and slender bodies like fuselage, launch vehicles must be examined such that they will not develop any aeroelastic instabilities within the specified flight regime. Aeroelasticiy is a science that deals wih an interaction between elastic, inertial and aerodynamic forces. Simulation of aeroelastic system involves coupled structural dynamics and aerodynamics, where analytical models are normally employed. Aerodynamic theories to build such analytical models of lifting surfaces and bodies are well established both in subsonic and supersonic regimes; however there is still not much confidence level achieved in the transonic regime to qualify any aerospace vehicle only through theoretical analysis procedures. Therefore, it becomes appropriate to use the experimental approach to evaluate the transonic aeroelastic characteristics of aerospace vehicles. In the last four decades, Aeroelasticity Group of Structural Technologies Division, NAL has carried out a number of aeroelastic testing projects and contributed immensely to the national aerospace programmes; to name a few LCA, SARAS, SLV, ASLV, PSLVand GSLV. Different kinds of aeroelastic problems have been addressed; both stabilty (flutter, divergence) and response (buffet) solutions are obtained experimentally. Indeed, during the last four decades, the model design and aeroelastic testing methodologies have been evolved to a matured state. Aeroelastic Testing (AET) has the following modules: 13; x2022; Deriving appropriate aeroelastic scale factors13; x2022; Design methodology (Equivalent or Replica)13; x2022; Simulation of boundary effect through model support system13; x2022; Fabrication of components and assembly procedures13; x2022; Non-structural mass simulation13; x2022; Instrumentation on the model and calibration of the sensors13; x2022; Qualification studies for both strength and stiffness13; x2022; Qualification studies for checking the dynamic simulation13; x2022; Wind tunnel testing13; x2022; Data analysis and results interpretation for the full scale vehicle13; AET plays an important role in understanding the aeroelastic behavior of any aerospace vehicle, which either operates at transonic regime or cross over it. This paper brings out our experiences that have been gained in the last four decades of testing the flight vehicles in 1.2m NAL trisonic wind tunne

Feasibility study of a spring support system for buffet models and a mini shaker for model excitation

To simulate free flight condition, an aeroelastic model has to be suspended on springs in the wind tunnel. This report describes the feasibility study of a leaf spring and a coil spring system for this purpose. Also the successful testing of a mini shaker for its capacity to excite the model in the tunnel for aeroelasuic damping measurement is reported

Characterization of piezoelectric stack actuators for structural control applications

In this paper we experimentally evaluate the response of several piezoelectric stack actuators under different loading conditions (mechanical, electrical and electromechanical). An improved smart material actuators measurement method suited for static and dynamic actuation is devised (Fig. 1). The output displacement of the active material is recorded under various prestress level and voltage values. The measurements indicate a strong dependence of piezoelectric properties under electromechanical loading conditions for the actuators. Results indicate that certain operating conditions (i.e., mechanical prestress) can improve actuation capabilities

Development of Active Engine Mount System using PZT Actuators for Low Speed Transport Aircraft

The progress of the first phase of project has been reviewed on October 2009. In this technical review, the design aspects of active struts and analysis result have been presented. The expert members have examined the feasibility of the active strut based AVC solution for the engine mount system. This report has narrated the technical details of the works so far carried out

Toxicity of pyrazinamide, administered once weekly in high dosage, in tuberculous patients*

The success of a twice-weekly regimen of streptomycin plus isoniazid, reported earlier from the Tuberculosis Chemotherapy Centre, Madras, prompted an investigation at the Centre of various once-weekly regimens of chemotherapy. In this context, a pilot study was undertaken in 19 patients to assess the toxicity of high-dosage pyrazinamide (70 mg/kg of body-weight), when administered once weekly, together with isoniazid (14 mg/kg of body-weight) and streptomycin (1 g), for at least 6 months. Serial estimations of SGOT and SGPT activity, urine tests for urobilin and bilirubin and haematological investigations were undertaken at frequent intervals. None of the patients showed any clinical evidence of hepatotoxicity; however, there was a slight and transient elevation in aminotransferase activity, probably of a non-specific nature, at 2 weeks. These findings are encouraging for the use of high-dosage pyrazinamide in once-weekly regimens of chemotherapy