Incoming Airflow Research Articles

Thrust Vector Observation for Force Feedback-Controlled UAVs

This paper presents a novel approach to Thrust Vector Control (TVC) for small Unmanned Aerial Vehicles (UAVs). The difficulties associated with conventional feed-forward TVC are outlined, and a practical solution to conquer these challenges is derived. The solution relies on observing boom deformations that are created by different thrust vector directions and high-velocity air inflow. The paper describes the required measurement electronics as well as the implementation of a dedicated testbed that allows the evaluation of mid-flight force measurements. Wind-tunnel tests show that the presented method for active thrust vector determination is able to quantify the disturbances due to the incoming air flow.

Design of an array of piezoresistive airflow sensors based on pressure loading mode for simultaneous detection of airflow velocity and direction.

As an irreplaceable element for obtaining airflow information in many engineering scenarios, airflow sensors have gained increasing attention across the fields of aerospace engineering, environmental engineering, sustainable energy exploitation, meteorology research, and so on. As one of the mainstream airflow sensing principles, piezoresistive airflow velocity sensors have experienced rapid growth over the years, while effective vector airflow sensors with the ability of detecting both airflow velocity and direction based on the piezoresistive principle are scarce. Here, on the basis of our developed piezoresistive airflow velocity sensors based on pressure loading mode, we design an array of these sensors and propose a corresponding explicit algorithm for simultaneous detection of airflow velocity and direction. This sensor array configuration enables an automatic recognition function of the quadrant of incoming airflow, which can significantly simplify the reverse calculation of airflow information compared with conventional vector airflow sensors. The experimental results demonstrate the decent performance of this sensor array for identifying both airflow velocity and direction. This study not only fills the gap between our developed airflow velocity sensor and the ability of detecting airflow direction but also presents a simple and universal array-based strategy for vector airflow sensing, which could be widely applied in airflow sensors based on other principles.

Вращательное и поступательное галопирование призм в воздушном потоке

In experiments in a wind tunnel, oscillations of three prisms with a rectangular cross section are studied. The prisms are located perpendicular to the velocity vector of the incoming flow and are limited from the ends by end plates that prevent air flow. The elastic suspension allows body oscillation with six degrees of freedom. It turned out that under the action of the air flow, two modes of oscillation of prism realized: translational oscillations in the direction perpendicular to the generatrix of prismatic bodies and the flow velocity, and rotational oscillations around an axis that is parallel to the generatrix, passes through the center of the prism and is perpendicular to the velocity of the incoming air flow. The tension of the two springs included in the elastic suspension is measured by the strain gauge method during the oscillation. The calibration experiment makes it possible to link the amplitudes of spring tension oscillations and phase shift with the amplitudes of rotational and translational oscillations of prisms. It turned out that a prism with a height-to-width ratio of 0.22 in the flow is subject to rotational oscillations. An increase in the ratio of height to width to 0.36 leads to a decrease in the amplitude of rotational oscillations and the appearance of translational ones. The ranges of existence of rotational and translational oscillations overlap. A further increase in the ratio of height to width to 0.43 is accompanied by intensive translational galloping.

Rotational and translational galloping of prisms in the air stream

In experiments in a wind tunnel, oscillations of three prisms with a rectangular cross section are studied. The prisms are located perpendicular to the velocity vector of the incoming flow and are limited from the ends by end plates that prevent air flow. The elastic suspension allows body oscillation with six degrees of freedom. It turned out that under the action of the air flow, two modes of oscillation of prism realized: translational oscillations in the direction perpendicular to the generatrix of prismatic bodies and the flow velocity, and rotational oscillations around an axis that is parallel to the generatrix, passes through the center of the prism and is perpendicular to the velocity of the incoming air flow. The tension of the two springs included in the elastic suspension is measured by the strain gauge method during the oscillation. The calibration experiment makes it possible to link the amplitudes of spring tension oscillations and phase shift with the amplitudes of rotational and translational oscillations of prisms. It turned out that a prism with a height-to-width ratio of 0.22 in the flow is subject to rotational oscillations. An increase in the ratio of height to width to 0.36 leads to a decrease in the amplitude of rotational oscillations and the appearance of translational ones. The ranges of existence of rotational and translational oscillations overlap. A further increase in the ratio of height to width to 0.43 is accompanied by intensive translational galloping. Keywords: galloping, bluff body, wind tunnel, strain gauge, translational oscillations, rotational oscillations.

Multifidelity simulation of underhood thermal system for a bus engine

This study performs a combined 0-dimensional/3-dimensional modelling approach to investigate the fluid flow and heat transfer characteristics of bus thermal management systems. The 3-dimensional model is deployed to develop new correlations for the heat transfer coefficient (Colburn-j factor) and the friction factor (Fanning-f factor) at the air-side of the multi-louver radiator and charge-air cooler. The effect of the fan operation is also taken into account. The existing correlations in the literature developed for cars where the radiator and charge-air cooler are placed in the front section of the vehicle exposed to a uniform incoming air flow. While in buses, these components are placed at the vehicle rear section and in contact with a turbulent and non-uniform air flow, highlighting the need for development of new Colburn-j factor and Fanning-f factor for air flow within the louvered fins in these two components. The coefficients developed are incorporated into the 0-dimensional model to predict the thermal characteristics of the bus underhood for a range of operating conditions. The 0-dimensional model simulates the heat interaction of the multiple thermodynamic systems. Thus, a better understanding of the thermal management is achieved by investigating the energy distribution within the engine compartment and describing the performance of the thermal systems. The 0-dimensional/3-dimensional model is examined under the peak brake power condition. A coolant mass flow rate of 3.74 kg/s and fans speed of 4000 rpm are the most optimum results since the coolant’s temperature is decreased by 5 °C and the parasitic losses are kept at minimum.

Investigation on the impact of the induced shock wave on the hydrogen mixing augmentation in a supersonic crossflow: A numerical study

The mixing process between the fuel and the incoming air flow plays an important role for the engineering implementation of a scramjet engine. In the current study, the shock wave/jet shear layer interaction approach is utilized to promote the hydrogen mixing enhancement in a supersonic flow. The action location between the induced shock wave and the air inflow, as well as the intensity of the shock wave, is investigated to capture the mixing enhancement mechanism. Some parameters are provided to evaluate the flow field properties quantitatively, namely the mixing efficiency and the total pressure recovery coefficient. The obtained results predicted by the three-dimensional Reynolds-average Navier-Stoke (RANS) equations coupled with the two-equation shear stress transport (SST) κ-ω turbulence model show that the shock wave/jet shear layer interaction approach can effectively improve the mixing efficiency. The mixing speed and the mixing efficiency both increase with the increase of the intensity of the shock wave. The mixing enhancement mechanism is that the enhancement of the streamwise and spanwise vorticity upstream of the jet promotes the enlargement of the upstream separation zone and recirculation zone. When the shock wave position moves downstream, the spanwise vorticity increases, and the downstream recirculation zone increases significantly to promote mixing.

Improving the efficiency of carousel wind turbine using aerodynamic shield

The problem of increasing the efficiency of using the oncoming air flow for a wind wheel with a vertical axis of rotation, which is a mechanical drive of the wind heat generator, is considered. It is proposed to increase the efficiency of the device by installing an aerodynamic shield for the air flow oncoming the wind wheel. Such a shield is a cylindrical body in which a heat generator is placed. The shield creates an effect of confuser, leading to an increase in the speed and, consequently, in the kinetic energy of the air flow acting on the rotor blades. It is shown experimentally that the presence of an aerodynamic shield under the conditions of the experiments carried out at an incoming air flow velocity of ~ 1 m/s leads to a practical doubling of the wind wheel torque.

Evolution of turbulent boundary layer over a three-dimensional bump

A bump is typically used in the inlet system of an aircraft engine to compress the incoming airflow and to reduce boundary layer thickness developed over fuselage. In this work, the turbulent flow over a three-dimensional bump is experimentally studied. The bump model is mounted in a closed return wind tunnel operated at the nominal velocity 10 m/s, corresponding to a friction Reynolds number of 2300. The flow field upstream the bump, along the bump centerline and at two different spanwise planes is measured with Particle Image Velocimetry (PIV). It is observed that a favorable pressure gradient develops until the suction peak of the bump, and that the average turbulence intensity within boundary layer is attenuated due to this favorable pressure gradient. The boundary layer thickness identified by examining profiles of streamwise velocity decreases significantly along the bump. The wall-normal position of the Turbulent/Non-Turbulent Interface (TNTI) identified with the vorticity criterion is also observed to decrease along the bump. When studying the behavior of the boundary layer thickness at different spanwise positions, we found that it tends to be larger in planes away from the centreline, which suggests that the bump diverts the flow.

Performance characterization of air mixing devices for square ducts

• Static air mixing devices designed for square ducts were investigated. • Mixing and hydraulic performance of air mixing devices were evaluated. • Effects of design and operating parameters on mixing performance were determined. • Mixing patterns for the mixers tested were examined. Considering that square ducts are widely utilized for HVAC system performance testing, air mixing devices designed for such ducts were experimentally investigated. The results of these studies can also inform field application of mixers, such as in airside economizer applications of rooftop air conditioning equipment. Three types of air mixing devices were considered; one was a louvered-type mixer designed based on ASHRAE Standard 41.2, and the others were an orifice mixer and an orifice-target combination mixer. With thermally maldistributed airflow, the mixing and hydraulic performance of the mixing devices were evaluated for various testing parameters including flowrate, flowrate ratio, overall mixing length, mixer spacing, mixer orientation, orifice diameter, and orifice-target spacing. The results indicate that all mixing devices tested were capable of reducing stratification of the airflow. It was found that the mixing effectiveness, in general, increases as the overall mixing length and/or for dual mixers, spacing, increase. For an overall mixing length of 2.0 duct diameters (D h ), which is the maximum mixing length for industrial use, the mixing effectiveness values of the louvered mixer, orifice mixer, and orifice-target mixer were 76.3, 75.1, and 69.9%, respectively. The pressure drop of the orifice-type mixers was significantly larger than for the louvered mixers. The results also indicate that in order to achieve more than 70% mixing effectiveness, the louvered mixers require a mixing length of 2.0 D h while the mixing length required for orifice-type mixers varies from 1.0 to 3.0 D h depending on the orifice hole diameter (0.4–0.6 D h ). Furthermore, it was found that the louvered-type mixers are less affected by total flowrate and the level of velocity maldistribution of incoming airflow than orifice-type mixers are. Additionally, orifice mixers cause substantial velocity maldistribution downstream of their location. This study provides insight into the comprehensive information on the performance and design of air mixing devices available for square ducts in addition to the literature in which most of the data are based on studies conducted under round ducts and relatively long mixing length conditions.

Nocturnal Rainfall East of the Antilles Islands

ABSTRACT We analyze nocturnal rainfall caused by the interaction of trade winds and land breezes on the windward flank of the islands of Guadeloupe, Dominica, and Martinique of the eastern Caribbean Antilles. Climatology for the 2000–2019 period and a nocturnal rainfall case study 8–9 February 2018 are supplemented by modern 5–25 km hourly resolution satellite and reanalysis products and station measurements that describe the diurnal cycle around the islands. Mean trade winds of 7 m s−1 decelerate upstream, ∂U/∂x less than −10−5 s−1, causing an increase in warm-cloud rainfall from 2 to 4 mm d−1 between 03:30 and 06:30 local time (local time is UTC-4). The incoming airflow has a characteristic Froude number less than 1 and stagnates on the windward slopes of these volcanic islands. Nocturnal land breezes spread toward the east coast about one-third of the time. Additional work considers whether air–sea interactions play a role. Low salinity and wave-induced turbulence to the east of the Antilles add buoyancy and moisture to the atmospheric boundary layer. Yet areas of low turbidity encircling the east Antilles suggest that nocturnal airflow creates a divergent “cushion” around Guadeloupe, Dominica, and Martinique. Thermal and orographic influences merge and rain falls over the eastern flank of the islands, contributing to the water resources.

Hermes - Wind Energy Harvesting Wireless System for Sensing AoA and Wind Speed

In this letter, we present Hermes - a novel, low-cost, wireless, batteryless, energy harvesting system for aerial vehicles for sensing wind speed and Angle of Attack (AoA) concurrently. Hermes comprises a set of piezoelectric films which flutter due to incoming wind and the characteristics of this aeroelastic flutter are utilized for determining the wind speed and AoA of the head-wind. Note that in our work we restrict the notion of flutter to high frequency oscillations due to incoming air flow. Hermes consists of five piezoelectric flags that are mounted on rigid clamps specifically placed at different angles. We designed Hermes to maximize the sensing performance and energy harvesting capability simultaneously, without compromising either accuracy or harvesting efficiency. Our current prototype can harvest the power of 440 μW on average. Over a wide range AoA from -10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> to 30 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> , the estimation of the wind speed is within 0.7 km/h error with 90% probability, and AoA error is within 1.2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> with 90% probability. Since Hermes necessitates no wires and batteries and is a low-cost sensor, it is well suited for a range of UAVs, gliders, and aircraft, which require flexible sensor placement and do not require new wiring, which is often complex in aircraft. Hermes is the first of its kind that exploits piezoelectric energy harvesting to simultaneously sense AoA and wind speed. This work is expected to open up new avenues for interdisciplinary research on embedded computing devices for aerospace applications.

Features of the thermal regime formation in the downcast shafts in the cold period of the year

In the cold period of the year, to ensure the required thermal regime in underground mine workings, the air supplied to the mine is heated using air handling systems. In future, the thermodynamic state of the prepared air flow when it is lowered along the mine shaft changes due to the influence of a number of factors. At the same time, the processes of heat and mass exchange between the incoming air and its environment are of particular interest. These processes directly depend on the initial parameters of the heated air, the downcast shaft depth and the presence of water flows into the mine shaft. Based on the obtained experimental data and theoretical studies, the analysis of the influence of various heat and mass transfer factors on the formation of microclimatic parameters of air in the downcast shafts of the Norilsk industrial district mines is carried out. It is shown that in the presence of external water flows from the flooded rocks behind the shaft lining, the microclimatic parameters of the air in the shaft are determined by the heat transfer from the incoming air flow to the underground water flowing down the downcast shaft lining. The research results made it possible to describe and explain the effect of lowering the air temperature entering the underground workings of deep mines

Influence of upstream angled ramp on fuel mixing of hydrogen jet at supersonic cross flow

The fuel injection system is a highly significant process in the design of the scramjet engine. In this paper, the presence of the upstream ramp edge on fuel distribution of jet flow at supersonic air stream of Mach = 4 is fully investigated. RANS equations are coupled with SST turbulence scheme to model the flow feature and diffusion of the fuel jet flow in attendance of angled ramp edge. The main emphasis of this study is to analyze fuel mixing and penetration of a single hydrogen jet in the presence of an upstream ramp at supersonic cross-flow. The size of the mixing zone at different angles of the ramp is investigated. Our results show that the application of the upstream ramp substantially influences the incoming supersonic airflow and changes the strength of vortices close to the jet. Our results show that the mixing performance of the ramp angle is 45% more than the slope angle. Increasing the slope and ramp angle from 10 deg to 30 deg increases the fuel mixing up to 55% downstream of the fuel jet.

Mechanical Valves for On-Board Flow Control of Inflatable Robots.

Inflatable robots are becoming increasingly popular, especially in applications where safe interactions are a priority. However, designing multifunctional robots that can operate with a single pressure input is challenging. A potential solution is to couple inflatables with passive valves that can harness the flow characteristics to create functionality. In this study, simple, easy to fabricate, lightweight, and inexpensive mechanical valves are presented that harness viscous flow and snapping arch principles. The mechanical valves can be fully integrated on‐board, enabling the control of the incoming airflow to realize multifunctional robots that operate with a single pressure input, with no need for electronic components, cables, or wires. By means of three robotic demos and guided by a numerical model, the capabilities of the valves are demonstrated and optimal input profiles are identified to achieve prescribed functionalities. The study enriches the array of available mechanical valves for inflatable robots and enables new strategies to realize multifunctional robots with on‐board flow control.

Nozzle Flow Simulation by Small Disturbance Approximation and Euler Method

The nozzle is a kind of equipment with a wide range of usage in the aerospace industry, of which its performance is vital for rocket engines by changing the geometry of the inner wall of the pipe section to accelerate the airflow. There are two types of nozzles commonly used: one is a tapered nozzle, and the other is a Laval nozzle. To analyze the flow phenomenon in nozzle is vital before transferring prototype design into industrial production, whether by laboratory experiment or computational simulation. In this paper, two different numerical methods are adopted to simulate gas behavior inside a simplified nozzle with upper and bottom symmetrical bumps. The first is to solve one dimensional Euler equations, and the other is to solve a scalar variable named velocity potential with small disturbance equations (SDE). The solutions under various inlet Mach numbers are compared by analysing the velocity fields and Mach number contours obtained by these two approaches. Similarities and differences between the Euler method and the potential SDE method for subsonic flow and supersonic flow are the key emphases in this work. For either subsonic or supersonic flow, the Mach number distribution along the nozzle’s center line shows a consistent trend for both methods. In contrast, the values of maximum or minimum Mach number have corresponding differences. Moreover, by using potential SDE simulation, several types of shock waves are successfully captured. All results show that the incoming airflow decelerates at the leading edge of the nozzle then accelerates when passing through the bumps, and finally decelerates back to the speed of inlet flow. The difference is that flows with varied Mach numbers has distinct velocity distributions in the nozzle.

Models for Generating and Processing of Signals of the Panoramic Sensor of Aerodynamic Angle and True Airspeed

The importance of information about the true airspeed and aerodynamic angles of aircraft and replenishment of arsenal of their measuring means with only electronic design scheme, low weight and cost, providing a panoramic measurement of the gliding angle is noted. It is shown that traditional measuring means of true airspeed of AP, which implement the aerodynamic and vane measuring methods of parameters of incoming air flow, using receivers and sensors distributed over the fuselage, have a complex design, significant weight and cost, and limited ranges of measuring aerodynamic angles, which limits their use on small-sized aircraft plane. The integrated sensor of aerodynamic angle and true airspeed, which implements a vortex method for measuring the parameters of incoming air flow, is considered. A single fixed flow receiver simplifies the design, and the time-frequency primary informative signals reduce the errors of instrumentation channel. The limited range of measurement of the gliding angle limits the use of the sensor on small AP. The integrated sensor of aerodynamic angle and true airspeed, which implements the ion-mark method for measuring the parameters of incoming air flow, is considered. The sensor provides a panoramic measurement of aerodynamic angle using receivers distributed in the measurement plane. But the multichannel measuring circuit significantly complicates the design, increases the weight and cost of the sensor, which limits its use on small-sized aircraft plane. The functional scheme of the original panoramic purely electronic sensor of the aerodynamic angle and true airspeed with one fixed receiver of the incoming air flow and ultrasonic instrumentation channels is revealed. Analytical models of the formation, processing and determination of the aerodynamic angle and true airspeed using frequency, time-pulse and phase informative signals are obtained. The analysis of the variants of used informative signals determines the prospects of using of the panoramic sensor with frequency informative signals on small-sized aircraft plane, in which there are no methodological errors from the influence of the ambient temperature when changing the flight altitude.

Dynamic Analysis of a Novel Quadruple Combined Cycle Based on Integrated Solar Tower-Gas Turbine-Supercritical CO2 and Organic Rankine Cycles

Abstract In this article, a novel quadruple cycle for power generation is presented. It consists of a gas turbine cycle, a Brayton cycle of supercritical carbon dioxide, a Rankin organic cycle with a cyclopentane working fluid, a Rankin steam cycle, a central tower, and a heliostat solar field. Because of improving the Brayton cycle's performance, supercritical carbon dioxide and the Rankine organic cycle have been added to the system. A solar tower system has been used to heat the incoming airflow to the combustion chamber. The heat generated by the solar tower in the first part increases the gas turbine cycle's air temperature, and in the second part, the water vapor heats the Rankin steam cycle. Due to solar radiation instability, the proposed system's performance is dynamically examined every hour of the year, and the results are reported. The thermodynamic simulation results are validated by thermoflex software and reference case with high accuracy. In this regard, energy, exergy, exergoeconomic, exergoenvironmental, emergoeconomic, and emergoenvironmental (6E) analyses have been performed for this system. The result indicates that the gas turbine cycle's fuel consumption is reduced by about 9% to 1.53 kg/s with the solar system's addition. Using solar energy and the Rankin steam cycle, the cycle's production capacity will increase from 43 MW to 66 MW.

Decentralized Control of Nanosatellite Tetrahedral Formation Flying Using Aerodynamic Forces

A decentralized control algorithm for the construction of a tetrahedral configuration using differential lift and drag forces is proposed in this paper. Four 3U CubeSats launched in LEO are considered. Satellite attitude-controlled motion relative to the incoming airflow provides the required differential forces in order to change the relative translational motion. The developed control algorithm allows one to track the relative reference trajectories for the satellites at the vertices of the tetrahedron of the required shape and size. The influence of the initial launch conditions on the controlled tetrahedral motion is studied in this paper.

Aerosol Generation in Ear Canal and Air‐Fluid Interface Suction

ObjectiveThe identification of aerosol-generating procedures (AGPs) is important during the current SARS-CoV-2 pandemic due to aerosol-mediated virus transmission. Aerosol measurement during clinical procedures using particle counting may be confounded by variable natural background aerosol levels or limited by partial volume sampling. The study objective was to quantify any significant aerosol generated from simulated suction clearance procedures.Study DesignProspective quantification of aerosol generation during clinical suction simulation.SettingClean chamber.MethodsWe created a clean environment for particle counting in a transparent neutralized polypropylene chamber. Air was passed through a HEPA 14 class filter to maintain a constant chamber inlet pressure. An optical particle counter was connected in line to the chamber exhaust vent to measure all of the vented particles. The chamber background count was 1 particle ≥0.3 µm per 15 minutes at a flow rate of 1 chamber air change per minute. We used this system to quantify very low aerosol counts generated from suction clearance of a silicone ear canal and at an open air-fluid interface.ResultsNo clinically significant aerosol generation was found by particle counting of the whole chamber air volume during simulated suction procedures.ConclusionSimulated ear suction clearance and air-fluid interface suction does not generate any significant aerosol. It appears likely that any aerosol potentially generated at the suction tube tip is entrained by incoming air flow. This is the first study to quantify aerosols generated by suction in a controlled environment; further research is required to determine its clinical implications.

The Efficacy of Lingual Laser Frenectomy in Pediatric OSAS: A Randomized Double-Blinded and Controlled Clinical Study.

This randomized, double-blind and controlled clinical trial investigates how a diode laser lingual frenectomy can improve obstructive sleep apnea syndrome (OSAS) in pediatric patients. Background: Several authors have shown that a short lingual frenulum causes a reduction in incoming air flow and the relationship between OSAS and a short lingual frenulum. Methods: Thirty-two pediatric patients were equally randomly divided into a Study Group (SG) and a Control Group (CG). On each SG patient a polysomnography 1 (PSG1) and a lingual frenectomy were performed using a diode laser via Doctor Smile Wiser technology, power 7 W. After three months, a new polysomnography (PSG2) was performed to evaluate the lingual frenectomy efficacy in pediatric patients. The pain was assessed by a numerical rating scale (NRS) before and after surgery. The CG followed the same protocol without a lingual frenectomy but myofunctional and speech therapy were conducted to qualitatively and quantitatively improve the lingual functionality. In the SG, eight subjects (50%) had severe OSAS and eight had moderate (50%) while in the CG, three subjects had severe OSAS (18.8%) and thirteen had moderate (81.2%). Results: In the SG, 93.8% were classified as mild OSAS and 6.2% as moderate. In contrast, in the CG, 18.75% were classified as mild OSAS, 62.5% as moderate and 18.75% as severe. Conclusion: The study demonstrates how a lingual laser frenectomy can improve OSAS in pediatric patients.