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Optical properties of transparent wood composites prepared using transverse sections of poplar wood
No full textThe revolutionary transformation of opaque wood into a transparent material, with combination of high optical transmittance and high haze, has gained widespread interest in the realms of advanced functional materials. However, the thickness of transparent wood composite (TWC) is limited to a few millimeters which restricts potential use. In this study, TWC were prepared using transverse sections of poplar (Populus deltoides) in thickness ranging from 1.5 to 15 mm by lignin modification bleaching followed by epoxy resin infiltration. The effects of bleaching duration as well as sample thickness on the optical properties of TWC were investigated. TWC was characterized using scanning electron microscopy and FTIR spectroscopy. The optical properties of TWC were measured using UV-VIS-NIR spectroscopy. The results indicated that light transmittance depended on severity of bleaching, lignin content and sample thickness
Simulation Studies Related to COVID-19 Pandemic
No full textThe latest COVID-19 pandemic has forced most of the countries to in state lockdown since there was no antidote for this virus until recent vaccine launch from Pfizer. Protecting from the virus only achieved by keeping social distance, wearing masks and ensuring personal hygiene. While the entire world is facing this pandemic together and the war against COVID is now multidisciplinary, there are new variant for virus is formed which has 70% more spreading capacity than the current one and hence it is extremely important to practice the self-precaution mentioned above. A detailed simulation analysis on such prevention practices such as ventilation systems, social distances and respiratory mask simulations has been done in this chapter. In addition to that some of the antiviral material that can be used for antiviral mask production has also been investigated in this chapter
Swept Fin-Induced Shock/Boundary-Layer Separation Control Using Corotating Vortex Generators
No full textAn experimental investigation was conducted to assess the effectiveness of an array of corotating and counter-rotating vanes in controlling a swept-shock-wave interaction induced by an 11 deg semi-infinite sharp fin in a Mach 2.05 flow. The control array was located all along the conical interaction line upstream of the swept interaction. For the corotating configuration, a parametric study was conducted to access the variation in 1) height of h∕δ 0.3, 0.5, and 0.75; 2) vane angle of α 18, 24, and 30 deg; and 3) vane spacing s on control effectiveness. For the counter-rotating configuration, only the effect of the vane height was studied. The array of corotating rectangular vane vortex generators (VGs) with closely spaced vanes of s 1h significantly reduced the plateau pressure in the entire interaction region as compared to no control with a maximum reduction of 44% at 0.67R for h∕δ 0.5 and in a separation shock strength of nearly 70% at 0.67R for h∕δ 0.75. Contrary to the corotating VGs, the counter-rotating VG array significantly pushed the separation line downstream in the conical interaction zone: the effect of which increased with an increase in vane height. This squeezing of the swept flow toward the fin significantly increases the plateau pressure and the separation shock strength, respectively, and is not favorable. For h∕δ 0.75, the shock strength increases by 50% as compared to no control
Failure Analysis of a Welded AISI321 Steel Bleed Air Connector of an Aircraft Engine
No full textFailure investigation was conducted on a bleed air connector of an aircraft engine that developed an opening during service. The connector was a fabricated tubular structure wherein the flanges were circumferentially welded to a bent pipe on both the ends. The flanges and the pipe were made of austenitic stainless steel AISI 321. Fractography study confirmed that the connector had failed by fatigue mechanism. Fatigue crack had initiated at one of the weld joints. The exact location of the crack initiation was at the weld-to-tube interface. After initiation, the crack had propagated into the pipe resulting in loss of material by fracture. Investigation revealed that the primary cause of fatigue crack initiation in the connector was stress concentration at the weld joint resulting from improper weld joint design. Inferior quality of weld was another factor that contributed to the failure. A detailed analysis of the failure is presented in this article and remedial measures suggested for preventing recurrence of similar failures
Effect of Passive Flow Control Devices on Base Pressure for Mach Numbers Between 0.5 and 1.4
No full textExperimental studies are carried out on an axisymmetric cylindrical base body for six freestream Mach numbers between 0.54 and 1.41. Unsteady pressure is measured on the base surface using high-frequency response Kulite pressure transducers. The effect of passive flow control devices on the mean base pressure and the unsteady characteristics of base pressure have been studied. A blunt base, a conventional cavity device, and three different ventilated cavity devices have been tested along with four different rounded base lip devices. A total of 20 different base geometric modifications are tested at 6 freestream Mach numbers resulting in 120 test cases. The cavity devices improve the base pressure as compared to the blunt base case, particularly for freestream Mach numbers more than 0.98. Among all the cases considered, a maximum increase of 8.6% in the base pressure coefficient is noticed for the normal ventilated cavity device as compared to the blunt base case for freestream Mach number of 1.22. The power spectral density of base pressure fluctuations revealed the dominant peaks on the base surface. The Strouhal number associated with the coherent structures developing in the shear layer varies between 0.2 and 0.27 for the six freestream Mach numbers considered. In the presence of cavity devices, dominant peaks are observed for Strouhal numbers between 1 and 5. The root-mean-square, skewness, kurtosis of the base pressure fluctuations for all the cases are presented. Maximum reduction in base pressure fluctuation is observed for the normal and inclined ventilated cavity device configuration test cases
Application of Phase-Averaging Methods to Sweeping Supersonic Jets
No full textThis paper examines various methods for phase averaging the flowfield of a sweeping supersonic jet emanating from a
scaled fluidic oscillator. Determination of the phase-averaged flowfield is challenging, especially at high oscillation frequencies where there is a jitter in the periodicity caused by its inherent fluid dynamics. Several phase-averaging approaches (including mathematical, signal processing, and phase-lock techniques) applied to time-resolved schlieren images of the flowfield are described. Criteria for evaluation are based on the image distribution per phase bin, the centerline intensity profile of the phase-averaged schlieren image, and the cross correlation of the images with the timeaveraged reference image. Examination of the different methods based on the criteria shows that the zero-crossing method is sufficiently accurate and most suitable for the naturally oscillating flowfield investigated in this study. Although the phase-locked approach works well at specific phase angles, overall, it is found unsuitable for the current test conditions. The zero-crossing method applied to a sweeping supersonic jet schlieren reveals shock structure distortion when switching directions in the oscillation cycle. Results indicate that the zero-crossing method described in this study can also be extended to other non-time-resolved quantitative and qualitative flowfield measurement techniques using a simultaneously acquired time-resolved reference signal
Aeroelastic Aspects of Axial Compressor Stage With Self-Recirculating Casing Treatment
No full textFor successful implementation of casing treatment designs in axial compressors, apart from the stall margin improvement benefits, aeroelasticity also plays a major role. This manuscript addresses the not often discussed aeroelastic aspects of a new discrete type of passive self-recirculating casing treatment (RCT) designed for a transonic axial compressor stage. Experiments are carefully designed for synchronized measurement of the unsteady fluidic disturbances and vibrations during rotating stall for compressor with baseline solid casing and self-RCT. The modal characteristics of the axial compressor rotor-disk assembly are studied experimentally and numerically. Experimentally it is observed that the rotating stall cells excite the blades in their fundamental mode in a compressor with baseline solid casing at the stall flow condition. In contrast, there is no excitation of the blades in the compressor with self-RCT at the same solid casing stall flow condition. Also, the self-RCT compared to the solid casing can significantly reduce the overall vibration levels of the blades that are excited at the stall flow condition. The casing treatment is able to alter the flow field near the tip region of the rotor blade, and hence influencing the forcing function of the rotating cantilever blades to have the aeroelastic benefit
Exploration of Inorganic Materials with Antiviral Properties
No full textThe infectious diseases by viruses have led to global health concern. Currently, world is experiencing the outbreak of SAR-CoV-2 (2019-nCoV). Efficient treatment of the viral infection is the utmost priority. Virus has the capacity of destroying the host cell and replicating inside it which poses a hindrance in the development of the antiviral drugs. In the current scenario, research has been carried out exploring the diagnosis, prevention and treatment of the viral infection. Many approaches are reported which includes antiviral procedures and methods according to the protocols. Nanotechnology has been considered to be promising due to its ability of dealing with the disease in an effective manner and by resolving the limitations of the traditional antiviral drugs. The research studies focus on the progress of the wide utilization of the antiviral drugs which have potential efficiency for combating the emerging viruses. Cost-effective, easy to synthesize effective antiviral drugs, could lessen the burden of the challenges faced worldwide due to the COVID-19 pandemic
Performance evaluation of different micro vortex generators in controlling a flare-induced shock–boundary layer interaction
No full textThis study evaluates the ability of five micro vortex generator (MVG) geometries in attenuating the flow separation induced by an axisymmetric compression corner. Experimental and computational investigations were carried out at Mach 2 on a cone–cylinder–flare model, with a flow deflection angle of 24° at the cylinder/flare juncture. The MVG shapes considered were baseline ramp, trapezoidal ramp, split ramp, thick vanes and ramped vanes. A circumferential array of these MVGs having a device height (h) of 1.4 mm and an inter-device spacing of 10.5 mm (7.5 h) was introduced 50 mm upstream of the compression corner. Streamwise counter-rotating vortex pairs that originated from these devices created alternate bands of upwash and downwash regions in the incoming boundary layer, which resulted in suitable three-dimensional alterations of the separation region’s size. Furthermore, surface streamline visualizations showed that the vortices induced profound topological transformations in the separated flow structure. In the absence of MVGs, spectral analysis of the pressure signal obtained from the separation shock’s intermittent region revealed a relatively broadband dominant frequency range of 0.55 kHz–0.9 kHz. The MVGs did not cause any significant change in the dominant frequency, but made the bandwidth slightly narrower. Among the different MVG designs that were studied, the ramped vanes (RV) induced the most momentum augmentation in the near wall region and thereby caused the maximum downstream shift in the separation shock’s position
Electronic, nanomechanical and smart reversible phase transition behaviours of sputtered titanium oxide-vanadium oxide composite thin films
No full textCrystalline vanadium oxide-titanium oxide (VO-TO) composite thin films of 197 nm are developed on quartz and silicon substrates by RF magnetron sputtering technique. A thorough structural investigation of deposited thin films is carried out by field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) techniques. Differential scanning calorimetry (DSC) and temperature-based sheet resistance measurement techniques reveals the Smart (i.e., reversible) phase transition behaviour of VO-TO films at about 45 °C. Further selective depth analysis by XPS on the VO-TO films shows the variation of the Ti doping amount along the thickness. The top region of VO-TO thin film possess lower Ti species, while beyond 50 nm thickness from the surface possess comparatively rich Ti species. This graded Ti species along the depth also results in the variation of nanomechanical properties along the depth as confirmed by nanoindentation. The simulation through the finite element approach is also carried out to depict the experimental results of nanoindentation. The nanohardness and modulus of the presently developed VO-TO composite film were measured as 6.7 GPa and 158.7 GPa, respectively at 50 nm depth. Beyond 50 nm, nanohardness and modulus were 5.6 GPa and 116.6 GPa, respectively. Further, finite element simulation predicted yield stress value of 3.52 GPa at 50 nm depth whereas higher yield stress of 4.68 GPa was predicted beyond 50 nm