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A successive robust flutter prediction technique for aeroelastic systems using µ method
No full textIn this work, a successive robust flutter prediction technique is developed by coupling nominal analysis, ground vibration test, wind tunnel test, uncertainty model updation and robust analysis based on the structured singular value method to predict the worst flutter boundary of a swept back wing in transonic flow regime. Here, uncertainties in both structural and unsteady aerodynamics parameters are considered in the generalized coordinates. These uncertainties are introduced in the nominal aeroelastic system in a linear fractional transformation framework. The magnitudes of structural uncertainties are estimated based on the difference in natural frequencies between ground vibration test and nominal analysis. The magnitudes of aerodynamic uncertainties are estimated using a model updation technique based on the structured singular value method considering the difference in damping values between wind tunnel test and nominal analysis. The capability of the present successive robust flutter prediction technique is investigated by estimating the robust flutter boundary of a swept back wing in transonic flow regime. From the results, it is observed that the uncertainty model updation provides a reasonable estimate of aerodynamic uncertainty magnitude. Further, the present flutter prediction approach gives a good estimate of transonic flutter boundary (transonic dip) by successively updating the aerodynamic uncertainty bounds using wind tunnel data for various set of test Mach numbers
Topological modifications due to ramped vanes in a flare-induced shock–boundary layer interaction flowfield
No full textEffect of 0ramped vane0-type vortex generators on a shock-induced flow separation in the vicinity of an axisymmetric compression corner was evaluated. Numerical simulations were performed at Mach 2 on a cone–cylinder–flare model with a flare angle of 24�. The undisturbed boundary layer thickness (d) at the location of the compression corner was 5 mm. A single array of these vortex generators with a device height
of 0.28d (1.4 mm) was placed on the cylinder surface at different streamwise positions, viz. 5d, 10d and 15d
upstream of the compression corner, and their ability to manipulate the shock–boundary layer interaction flowfield was compared. The presence of these devices caused substantial changes in the interaction region and the separation bubble structure. The separation bubble transformed into a series of spade-shaped structures with pockets of attached flow in between them. The ramped vanes increased the separation length along the device centreline, but this effect was attenuated considerably, by bringing them closer to the interaction region. Moving the ramped vanes closer also had a collapsing effect on the spade-shaped structures, which simultaneously widened the attached flow zones in between them
Neural Partial Differentiation-Based Estimation of Terminal Airspace Sector Capacity.
Get PDFThe main focus of this article is the online estimation of the terminal airspace sector capacity from the Air Tra� c Controller 0ATC) dynamical neural model using Neural Partial Di� erentiation (NPD) with permissible safe separation and a� ordable workload. For this purpose, a primarily neural model of a multi-input-single-output (MISO) ATC dynamical system is established, and the NPD method is used to estimate the model parameters from the experimental data. These estimated parameters have a less relative standard deviation, and hence the model validation results show that the predicted neural model response is well matched with the intervention of the ATC workload. Moreover, the proposed neural network-based approach works well with the experimental data online as it does not require the initial values of model parameters, which are unknown in practic
Solution combustion synthesis of calcium phosphate-based bioceramic powders for biomedical applications
No full textCalcium phosphate (CaP)-based bioceramics are widely used in orthopedics and dentistry for bone regeneration due to their good biocompatibility, osseointegration and osteoconduction. Synthetic hydroxyapatite (HAp) is the most widely used bioceramic coating in biomedical implants as it has a chemical composition similar to that of the bone. The properties of the coating depend on the nature of powders and in turn on the source of the powders. Hydroxyapatite powders can be prepared by a variety of chemical routes like co-precipitation, hydrothermal, sol-gel, solution combustion, etc. Among these methods, the solution combustion method is promising as it is a single step, cost-effective and energy-efficient process and yields high purity ceramic powders compared to conventional multi-step wet chemical processes. This method can also yield powders in nano and micron size range and can be used for the fabrication of coatings using methods like plasma spraying, suspension plasma spraying, electrophoretic deposition, etc. This chapter gives an overview of the solution combustion synthesis of pure and doped hydroxyapatite powders and their characterization. The last section of this chapter discusses the solution combustion synthesis of plasma sprayable hydroxyapatite powder, fabrication of HAp coating and characterization of the developed plasma-sprayed coating
Sprayable PEDOT:PSS based spectrally selective coating for solar energy harvesting
No full textA novel spectrally selective coating was developed on stainless substrates using commercially available poly(ethylene-3,4-dioxythiophene):poly (styrene sulfonate), (PEDOT:PSS) polymer for solar energy harvesting applications. An intrinsic (i.e., single) absorber layer concept was used to develop this coating. The as-prepared PEDOT:PSS dispersion was applied on substrates with thickness in the range of 0.1–5.8 μm using an automated spray deposition system, and the effect of thickness on the optical properties was studied in detail. The intrinsic properties of PEDOT:PSS resulted in high absorptance and low emittance, this was ascertained using glass, quartz and KBR pellets. With optimization of coating thickness, the reflectance edge shifted towards higher wavelength and near perfect absorption was obtained over a broad wavelength range leading to very high absorptance. The optimized PEDOT:PSS coating (approximately 5.8 μm thick) deposited on stainless steel substrates exhibited absorptance of 0.967 and emittance of 0.36
Characterization and microhardness of Ni−W−P coatings electrodeposited with gluconate bath
No full textNi−W−P coatings are electrodeposited from an acid gluconate bath and the effect of P addition to deposits is characterized by various physicochemical techniques. The effect of direct current (DC) and pulse current (PC) deposition modes on the structure, morphology, surface roughness, and elemental oxidation states of Ni−W−P coatings is studied in detail. X-ray diffraction (XRD) patterns of Ni−W−P coatings display the formation of an amorphous structure, which is influenced by the addition of phosphorus. Results obtained from field emission scanning electron microscopy (FESEM) images reveal the appearance of homogeneous coarse nodular morphology for electrodeposited Ni−W−P coatings devoid of cracks. X-ray photoelectron spectroscopy (XPS) studies of Ni−W−P coatings indicate the presence of metallic and oxidized Ni species in DC-plated coatings, whereas oxidized Ni species dominate in PC-plated coatings. Microhardness of as-deposited DC Ni−W−P coatings increases as the phosphorus content increases, whereas the microhardness is similar for all PC Ni−W−P coatings. The effect of heat treatment on the structure and microhardness of the deposits carried at different temperatures shows a substantial increase in microhardness which is comparable with hard chromium coating
Assessment of Flow Field Behind the Mechanical Vortex Generators at Mach 2.0
No full textExperiments were carried out at M∞ = 2.05 to understand the flow development downstream of the mechanical vortex generators. Four control devices were tested, (i) rectangular vane, MVG1 (ii) ramp vane, MVG2 (iii) Anderson vane, MVG3 (iv) split-Anderson vane, MVG4. The total pressure values were obtained through two rakes (each consisting of 12 pitot tubes) placed along three streamwise locations of z = 5δ, 10δ and 15δ (where δ = 12.5 mm is the local boundary layer thickness for no-control). The velocity contour shows well-defined wake region behind that of all the control configurations. The wake appears to lift off from the plate surface with the increase in the streamwise distance. The relative velocity contour captures the momentum re-distribution occurring between the outer edge of boundary layer and the near-wall region. The oil flow visualization for control highlights the presence of vortex trails, which for MVG1 appears to be larger than other control configurations. The boundary layer profile along the vortex trails showed fullness to the profile for MVG1, whereas for MVG3-4, there is minimal change relative to that of the no-control
Strain sensor's network for low-velocity impact location estimation on carbon reinforced fiber plastic structures: Part-I
No full textIn this work, we have investigated the strain response (angular/spatial) from fiber Bragg grating (FBG) sensor & resistance strain gauge (RSG) sensors bonded to the composite structure due to the projectile low velocity impact (LVI). The number of sensor & its orientating has been optimized based on such experimental data and designed an optimum sensor network for faithful LVI detection. In order to study the efficacy of the sensor network, an impact localization algorithm based on peak strain amplitude from the sensor bonded to the structure was used in this study. Further the detection efficiency of the algorithm has been improved using weighted average value around the peak amplitude of strain experienced by the sensor. We found that for the high energy (~35 J) LVI the maximum distance error (Euclidian distance) was 50 mm for 80% of total trail case. Furthermore, we have developed and compared the relative performance of the algorithm cited in the literature, will be presented in PART-II of the same Journal
Facile synthesis of CuCr2O4/BiOBr nanocomposite and its photocatalytic activity towards RhB and tetracycline hydrochloride degradation under household visible LED light irradiation.
No full textHere we report the development of CuCr2O4/BiOBr nanocomposite photocatalysts for the first time to serve the purpose of rhodamine B (RhB) and tetracycline hydrochloride (TC-HCl) degradation using household visible light emitting diode (LED) light. In this nanocomposite, sol-gel combustion made spherical shaped CuCr2O4 nanoparticles are decorated on BiOBr plates in single pot via precipitation method using cetyltrimethylammonium bromide (CTAB) as the Br source as well as the template. The present investigation highlights a significant advancement to tackle the challenge of visible light induced photocatalytic degradation of harmful organic dye RhB and antibiotic-pollutant TC-HCl. The 20%CuCr2O4/BiOBr nanocomposite exhibits high degradation activity for both RhB (96.0% in 15 min) and TC-HCl (96.7% in 300 min) in presence of LED light with good recycling characteristics. Detailed structural and optical characterization using XRD, BET, FESEM, TEM, HRTEM, EDX, XPS, UV−Vis DRS, PL spectroscopy and Raman spectroscopy have been carried out prior performing photocatalytic activity tests. The structural as well as optical data have revealed a significant improvement in visible light absorption of BiOBr in presence of CuCr2O4. Based on energy band modification at the heterojunction of nanocomposite materials and their radical trapping ability, a plausible mechanistic path of photocatalytic degradation is presented
Development of a retro-reflective screen-based large-field high-speed shadowgraph flow visualization technique and its application to a hydrogen-fueled valveless pulsejet engine
No full textLarge field flow visualization of the unsteady combusting flow inside a hydrogen-fueled valveless pulsejet engine has been successfully demonstrated by using a retro-reflective screen based high-speed shadowgraph technique. A rectangular cross-sectional valveless pulsejet engine with optical access has been designed, fabricated, and successfully used for demonstrating the effective use of a retro-reflective shadowgraph technique for large and spatially wide flow fields of interest. The aspect ratio of the engine considered for the study was 13.5 and the technique helped to understand the acoustically coupled combusting flow structures from the intake to the tailpipe of the pulsejet engine. A Photron FASTCAM SA4 camera was used in this study. High-speed shadowgraph videos were captured with a frame rate of 13500 frames per second with a resolution of 1024 × 272 pixels