Computational and Experimental Study for Reducing Forebody Wake Effect by Proper Designing of a Slit cut Square Parachute used for Sonobuoy Drop

This paper discusses the design of a square parachute based on classical approach, computational analysis and experimentation. This parachute will be used to drop directional sonobuoy on the sea to locate and classify the submarines. Design improvements are brought out by providing slits into a solid square canopy of parachute to bring in more stability and minimum drift during descend. Specifically, the effect of upstream sonobuoy, RANS model, suspension line length, canopy size and slit size in flow structure were considered. The predicted drag coefficients obtained from CFD for square canopy with slit-cuts compared with the results of wind tunnel experiment and found that the increase in the suspension-line length and/or of the surface area of the parachute canopy helps in better stability and results in the minimum drag loss.

Improved Accuracy of a Single-Slit Digital Sun Sensor Design for CubeSat Application Using Sub-Pixel Interpolation

In recent years, we have seen significant improvements in the digital sun sensor (DSS) design enabled by advanced micro-systems fabrication and optical sensing technologies. In this paper, we propose a simple single-slit DSS concept with improved accuracy using sub-pixel interpolation. In considering the DSS design, we focused on several characteristics of the sun sensor, including field-of-view, sensor accuracy, complexity, and computational requirements. First, the optimal mask design was determined based on the simple geometry of the slit size, mask height and pixel width. Then, a two-step pixel read-out algorithm was implemented for sub-pixel level interpolation to determine the illumination ratio using 1-, 2-, 4- and 8-bit readouts. Lastly, the improved DSS was integrated with typical CubeSat, commercial-grade attitude sensors suite and a simple TRIAD method to determine the attitude of a CubeSat in LEO. Compared to standard 1-bit read-out mode (0.32 deg RMSE), 8-bit DSS achieves better than 0.01 deg RMSE. In a CubeSat scenario, improvements in attitude knowledge and control accuracy are marginal when using TRIAD, due to the significantly lower accuracy in other CubeSat-scale sensors (magnetometer, for example).

Design and Fabrication of a Novel Window-Type Convection Device

Global warming, climate change, and ever-increasing energy demand are among the pressing challenges currently facing humanity. Particularly, indoor air conditioning, a major source of energy consumption, requires immediate improvement to prevent energy crises. In this study, various airfoil profiles were applied to create a window-type convection device that entrains air to improve convection between indoor and outdoor airflows and adjust the indoor temperature. How the geometric structure of the convection device affects its air entrainment performance was investigated on the basis of various airfoil profiles and outlet slit sizes of the airflow multiplier. The airfoil profiles were designed according to the 4-digit series developed by the National Advisory Committee for Aeronautics. The results revealed that airfoil thickness, airfoil camber, and air outlet slit size affected the mass flow rate of the convection device. Overall, the mass flow rate at the outlet of the convection device was more than 10 times greater than at the inlet, demonstrating the potential of the device to improve air convection. To validate these simulated results, the wind-deflector plate was processed using the NACA4424 airfoil with a 1.2 mm slit, and various operating voltages were applied to the convection device to measure the resulting wind speeds and calculate the corresponding mass flow rates. The experimental and simulated results were similar, with a mean error of <7%, indicating that the airfoil-shaped wind-deflector plate substantially improved air entrainment of the convection device to the goal of reduced energy consumption and carbon emissions.

Research on the physical model of features of the behavior of a two-phase bath at top blowing through a tip with folded nozzles

At the previous stage of research using a physical model of an oxygen converter, the results of studying the features of purging a single-phase liquid through a single composite nozzle were obtained. The aim of this work was to study the behavior of a two-phase bath using a multi-nozzle lance with folded nozzles. At this stage of the study, silicone oil was used to simulate the slag phase of a two-phase bath. The peculiarities of the influence of experimental nozzles on the processes of mixing and foaming of two phases were studied. Three variants of the experimental nozzle design were investigated: a combination of a conventional and a slit nozzle with a ratio of their areas of 1: 1, 1: 2 and 2: 1. It is established that the use of a tip with four nozzles during purging from above promotes the active formation of a two-layer foamed emulsion on the surface of the bath. Comparison of the operation of the tip with folded nozzles with a tip with a cylindrical indicates more active mixing of the two liquids and the formation of a more stable and much higher layer of foamed emulsion. The most favorable conditions for the organization of full mixing of the two phases in the converter bath are formed when using folded nozzles with a slit size of about 35% and a ratio of slot and nozzle area of 1: 2. To intensify the mixing processes in the upper zone of the unit, it is most expedient to use folded nozzles with a larger fraction of the slit (up to 65%) and the ratio of the areas of the components of the nozzle 2: 1. The use of nozzles with equal areas of components in the studied conditions does not have a positive effect on metabolic processes in the converter bath.

Effects of Slitting Size and Inlet Operating Conditions on Hydrogen Combustion Characteristics in a Micro-Combustor With a Controllable Vortex Slotted Bluff Body

Effects of controllable vortex slotted bluff body parameters (position of a bluff body, slit size, and controllable flow ratio) on the combustion characteristics of hydrogen/air in a micro-combustor with a bluff body were investigated numerically. The results illustrated that the combustion efficiency of hydrogen decreases with increasing distance (L1) between the front edge of the bluff body and the combustor inlet. The combustion characteristics of the micro-combustor are optimum when L1 is 0 mm. The blow-off limit of the combustor reaches a maximum (564 cm3/s) when the slit width (d) is 20% of the bluff body width. The blow-off limit first increases and then decreases when the equivalence ratio (φ) increases and reaches a maximum (732 cm3/s) when φ is 1.0, and the controllable flow ratio is 0.2. The combustion efficiency of hydrogen is gradually increased with the increase in the controllable flow ratio. When φ is less than 1.0, the optimal controllable flow ratio gradually decreases with the increase in the premixed gas flow rate, and the optimal controllable flow ratio basically remains at 0.6 when the premixed gas flow rate is less than 360 cm3/s.

Nanoscale Fluid Mechanics Working Principles of Transverse Flow Carbon Nanotube Membrane for Enhanced Desalination

This work introduces the transverse flow carbon nanotube (CNT) membrane, a novel membrane configuration designed to separate salt from water efficiently. The transverse flow CNT membrane uses transverse flow across horizontally stacked CNT, with neighboring CNT separated by a critical slit size. Through molecular dynamics (MD) simulation, the nano-fluidics interactions involved in the separation of salt from water using the transverse flow CNT membrane is studied. The simulation shows that this new membrane offers superior desalination performance, with permeability more than two times that of atom-thick graphene slit membrane, and orders of magnitude higher than conventional membranes. The effects of the nano-channels formed by the transverse flow CNT membrane on the behavior of water molecules and salt ions in a desalination system are studied in further detail with thermodynamic free energy computations, oxygen density mapping and hydrogen bond network studies. This simple but effective design offers an alternative solution for the practical use of CNT for efficient desalination.

Discrete-element investigation of influence of granular debris flow baffles on rigid barrier impact

Granular debris flow baffles are commonly installed in front of rigid barriers to dissipate flow energy and reduce the required barrier impact capacity. Despite the engineering value of baffles, their influence on rigid barrier impact is still not well understood. A previously calibrated discrete element method (DEM) model using a series of flume experiments was adopted to study the effectiveness of installing baffles in front of a rigid barrier. Froude scaling was used to characterize the flow front. Different baffle configurations were examined, namely number of rows, spacing between successive rows (L), and baffle height. Results reveal an optimum row spacing of L/D = 3 (D is the slit size). Row spacing less than L/D = 3 leads to increased peak dynamic force from overflow impacting the barrier, whereas row spacing greater than L/D = 3 results in increased peak dynamic force from the granular debris flow front. Increasing spacing greater than L/D = 3 allows the dispersion of debris between rows and decreases the effectiveness of the second row. Adopting baffle heights greater than 1.5 times the approach flow depth (h) reveals little influence on the peak impact force induced on the barrier.

Design and Shielding Effectiveness of Electromagnetic Shielding Textiles

.In order to design better anti-radiation and electromagnetic shielding fabric and the clothing and makes it maintained better of electromagnetic shield effectiveness, the influence of radiation source, radiation distance, anti-electromagnetic radiation material, fabric structure, gap size, holes area, clothing exposed area as well as the tunnel effect and so on the fabric radiation protection performance were comprehensively discussed in this article. As well, according to these influence factor analysis the regular conditions that the electromagnetic shielding fabric and garment design should be meet. The analysis result indicated that the shielding effectiveness of the fabric was decreased with the increase of the radiant frequency, the fabric slit size, the hole area and enhanced with the growing of the metal content, the organizational structure close degree as well as the radiation distance.In the case of the equal shielding effect, the bigger exposed area leads weaker electromagnetic shielding effectiveness and if the exposed area oversize can cause the shield effect vanished. Also the clothing shield potency was related to the opening radius, the length, the inside and outside dielectric constant, the permeability of the shirt or cuff. The comprehensive effectiveness of electromagnetic shielding fabrics will be gradually improved if they can meet these regular conditions continually.