Propeller Rotation Research Articles

Analysis of propeller wake field and vortical structures using [formula omitted] SST Method

CFD simulations are conducted to study the wake field behind a marine propeller in open water conditions at various advance coefficients. The local variables (velocity, pressure) and the wake structure characteristics are analyzed extensively using mean, Root Mean Square (RMS) and Fourier analysis of data. The integral variables (forces/moments) and their correlations with local variables are also investigated. Additionally, the iterative and grid verification studies are conducted to evaluate numerical uncertainty of the simulations. The results showed good agreement between the integral variables obtained by the simulations and those of experiments available in the literature, which confirmed the validity of the computational method employed in this work. Fourier analysis studies on integral variables showed that the rotation of the whole propeller determines the fluctuation of side forces at high J, while at low J, mostly rotation of individual blades affects the side forces. The local flow studies suggested strong correlation between the advance coefficient and the characteristics of vortical structures including their formations, trajectories, and stabilities.

Vibration Does Not Affect Short Term Outcomes Following Traumatic Brain Injury in a Porcine Model

Abstract Introduction Traumatic brain injury (TBI) has become increasingly prevalent among the injuries sustained in the military. Many wounded warriors require emergency medical evacuation via helicopter and subsequently fixed wing transport. During aeromedical evacuation, both pilots and patients experience whole body vibration due to engine, rotor, and propeller rotation. The impact of posttraumatic vibration and hypoxia exposure characteristic of the aeromedical evacuation environment on TBI is currently unknown. Methods A swine TBI model of controlled cortical impact was utilized. The pigs first underwent TBI or sham injury and were subsequently exposed to vibration or no vibration and hypoxia or normoxia for 2 hours. They were monitored for an additional 4 hours following vibration/hypoxia and blood was drawn at hourly intervals for cytokine and serum biomarker analysis. Continuous physiologic and neurologic monitoring were utilized. Prior to the conclusion of the experiment, the animals underwent brain magnetic resonance imaging. At the end of the study, the brain was extracted for histologic analysis. Results Physiologic parameters except for peripheral capillary oxygen saturation (SpO2) were similar between all groups. The hypoxia groups demonstrated the expected decrease in SpO2 and pO2 during the hypoxic period, and this was sustained throughout the study period. The pH, pCO2 and electrolytes were similar among all groups. Neuron specific enolase was increased over time in the TBI group, however it was similar to the sham TBI group at all time points. There were no differences in IL-1β, IL-6, IL-8, TNFα, GFAP, HIF1α, syndecan-1, or S100β serum levels between groups. The mean ICP during cortical impact in the TBI group was 279.8 ± 56.2 mmHg. However, the postinjury ICP was not different between groups at any subsequent time point. Brain tissue oxygenation and perfusion were similar between all groups. Conclusion In this novel study evaluating the effect of vibration on short-term outcomes following TBI, we demonstrate that the moderate vibration and hypoxia simulating aeromedical evacuation do not impact short term outcomes following TBI.

Underwater Object Localization using the Spinning Propeller Noise of Ships Based on the Wittekind Model

The purpose of this article is to localize underwater objects based on the noise reflection of the propeller rotation in cavitation mode. In the proposed method, the propeller noise, which plays the role of pings in active sonar, is modeled by the Wittekind method. As such, an echo is continuously received by a vertical and uniform linear hydrophone array due to reflection from the underwater targets. The challenges associated with the underwater channels are simulated by the ocean model in COMSOL. Specifically, to model the propagation of underwater acoustic in this channel, the Helmholtz equation is solved using COMSOL. Finally, localization is performed by comparing the Delay & Sum algorithm and the multiple signal classification (MUSIC) algorithm in MATLAB. According to the simulation results, the proposed method is able to detect the position of the target and the propeller approximately, although the multipath phenomenon causes adverse effects on the results. The narrowband MUSIC algorithm is used in the proposed method at the frequency of the strongest intensity.

Numerical investigation on aerodynamic performance of a ducted fan under interferences from the ground, static water and dynamic waves

Ducted fans have been widely applied in various VTOL (vertical takeoff and landing) vehicles due to their high efficiency and low noise. By using the sliding mesh technique to simulate propeller rotation, a ducted fan system is chosen and the effects of the ground, static water and dynamic waves on its aerodynamic performance are evaluated, thereby exploring the adaptability of the system to complicated environments. The ground is set to slip wall moving with the same speed as the free stream and the static water surface is identified by using the VOF model. To generate dynamic waves, the open channel wave boundary is investigated to simulate a Stokes wave combined with the VOF model. A series of calculation cases consisting of free space, the ground effect, the static water effect and the wave effect are observed and analyzed in detail. The results indicate that ground, water surface and wave can strongly affect the aerodynamic performance of the ducted fan, as they interrupt the jet flow from the outlet of the duct and further pull the rebounded flow into the system. A decrease in the height between the system and the surface leads to a greater influence on the ducted fan. The strong effect obtained by the rigid ground benefits the lift of the propeller the most but also greatly weakens the lift of the duct; ultimately, the total lift of the system is lost. The torque changes by a law similar to that of the lift. The soft water surface is impacted to form a “drainage area”, which can be considered to increase the distance between the system and the water. Therefore, the water effect is not as strong as the ground effect. However, the change rules of the lift and the torque are nearly the same as those for the ground effect. The dynamic wave has the most complicated effect on the system. The periodic wave causes unpredictable periodic changes on the lift and the torque of the duct and the propeller, which may be related to numerical wave attenuation and the real-time changes in the soft wave surface. A larger wave height and a shorter distance between the wave and the system lead to a greater influence on the ducted fan. Moreover, the dynamic wave can induce “dynamic uplift” and hysteresis phenomena on the aerodynamic performance of the system.

Influence of Ice Size Parameter Variation on Hydrodynamic Performance of Podded Propulsor

During ice-breaking navigation, a massive amount of crushed ice blocks with different sizes is accumulated under the hull of an ice-going ship. This ice slides into the flow field in the forward side of the podded propulsor, affecting the surrounding flow field and aggravating the non-uniformity of the propeller wake. A pulsating load is formed on the propeller, which affects the hydrodynamic performance of the podded propulsor. To study the changes in the propeller hydrodynamic performance during the ice-podded propulsor interaction, the overlapping grid technique is used to simulate the unsteady hydrodynamic performance of the podded propulsor at different propeller rotation angles and different ice block sizes. Hence, the hydrodynamic blade behavior during propeller rotation under the interaction between the ice and podded propulsor is discussed. The unsteady propeller loads and surrounding flow fields obtained for ice blocks with different sizes interacting with the podded propulsor are analyzed in detail. The variation in the hydrodynamic performance during the circular motion of a propeller and the influence of ice size variation on the propeller thrust and torque are determined. The calculation results have certain reference significance for experiment-based research, theoretical calculations and numerical simulation concerning ice-podded propulsor interaction.

Design and Control of Soft Unmanned Aerial Vehicle ‘S-CLOUD’

Short time-of-flight and safety concerns owing to low efficiency and fast rotation of propellers, respectively, are hurdles in the usage of drones. Usually, drones are carrying out missions that distant from the people like aerial photography, measurement, delivery, and surveillance, and, thus, it is not allowed to deploy drones above crowds. In this article, we present a novel soft drone called S-CLOUD that has longer time-of-flight (more than an hour) and higher user safety. It is composed of a torus-shaped envelope made of soft material, filled with Helium gas, and a center flow control unit mounted at the center of the envelope for producing translational ( $X$ -, $Y$ -, and $Z$ -axes) and rotational ( $Z$ -axis) motions. In this article, the control unit and envelope design are described in detail, and the characteristics of the drone are explained. Moreover, sensor-based feedback control algorithms and their experimental results are described. Finally, applications with S-CLOUD exhibiting its feasibility are also presented.

Unmanned Aerial Vehicle-Borne Sensor System for Atmosphere-Particulate-Matter Measurements: Design and Experiments.

An unmanned aerial vehicle (UAV) particulate-matter (PM) monitoring system was developed that can perform three-dimensional stereoscopic observation of PM2.5 and PM10 in the atmosphere. The UAV monitoring system was mainly integrated by modules of data acquisition and processing, wireless data transmission, and global positioning system (GPS). Particularly, in this study, a ground measurement-control subsystem was added that can display and store collected data in real time and set up measurement scenarios, data-storage modes, and system sampling frequency as needed. The UAV PM monitoring system was calibrated via comparison with a national air-quality monitoring station; the data of both systems were highly correlated. Since rotation of the UAV propeller affects measured PM concentration, this study specifically tested this effect by setting up another identical monitoring system fixed at a tower as reference. The UAV systems worked simultaneously to collect data for comparison. A correction method for the propeller disturbance was proposed. Averaged relative errors for the PM2.5 and PM10 concentrations measured by the two systems were 6.2% and 6.6%, respectively, implying that the UAV system could be used for monitoring PM in an atmosphere environment.

The Effect of Rudder Existence on Propeller Eccentric Force

In order to design a safe shafting system in a ship, it is vital to precisely predict load on stern tube bearing. It is well known that load on stern tube bearing is directly influenced by the eccentric force of a propeller. In this paper, the effect of rudder existence on propeller eccentric force was studied based on numerical analysis with a 10,000 TEU class container vessel. To obtain propeller eccentric force, numerical simulations including propeller rotation motion using a sliding mesh technique were carried out. When a ship is turning, propeller eccentric force significantly changes compared to those of straight run. For starboard turning especially, the propeller vertical moment was decreased by about 50% due to the existence of a rudder compared to that without a rudder. In contrast, as for port turning, the results of simulations with and without a rudder were similar to each other. This difference is fundamentally due to the interaction between the direction of propeller rotation and the inflow direction to a propeller. Based on this study, it is inferred that the influence of appendages around a propeller need to be considered to ensure the reliable prediction of propeller eccentric force.

Experimental and Numerical Investigation of DARPA Suboff Submarine Propelled with INSEAN E1619 Propeller for Self-Propulsion

The Defense Advanced Research Projects Agency (DARPA) Suboff Submarine propelled by the Italian Ship Model Basin (INSEAN) E1619 propeller is extensively used in submarine validation studies. Although there are several numerical studies where the DARPA Suboff submarine is used in combination with E1619 propeller there are no experimental data available in open literature for the self-propulsion condition. In this article, the self-propulsion characteristics of the DARPA Suboff submarine model with INSEAN E1619 propeller obtained with experimental and numerical methods are presented and discussed by means of Taylor wake fraction, thrust deduction, hull efficiency, relative rotative efficiency, and propulsive efficiency. To experimentally investigate the submarine form, a self-propulsion experimental setup is designed and manufactured. Resistance and self-propulsion experiments are conducted in Istanbul Technical University Ata Nutku Ship Model Testing Laboratory. Resistance tests are carried out for three different speeds, and the results show good agreement with the published experimental results. Propulsion tests are conducted by using the load-varying self-propulsion test method for constant speed and seven different propeller rotation rates. Rotational speed, thrust, and torque forces at self-propulsion point are investigated. For the numerical computations a commercial Computational Fluid Dynamics (CFD) code is used. Propeller open water characteristics and nondimensional velocities behind the propeller are calculated. Self-propulsion point of the submarine and propeller assembly is also solved numerically and the results are compared with the results obtained from the experiments, and it is seen that especially the propeller rate of revolution and thrust force are predicted with very good approximation.

Performance Comparison Between Ellipse and Circular Intake Shapes of Propeller Flow Cooling System (PFCS) with Numerical and Experimental Methods

This research carried out an analysis on the use of high pressure flow behind propeller to cool the ship main engine known as Propeller Flow Cooling System (PFCS). The system is commonly found on relatively small fishing boats at South Sulawesi area of Indonesia. Using the system, the special pump for engine cooling purpose is not needed. The present research conducted an investigation on PFCS intake shape that would be optimal for delivering water to main engine which was arisen from the propeller rotation and to find the difference of water capacity produced from different shapes of intake. The implemented research methods were numerical and experimental methods that analysed the shape of two intake shapes namely, circular and elliptical shapes. In numerical computation, ANSYS CFX software was adopted. The result from numerical computations was an initial prediction to the tendency of the results. In order to verify the results, an experiment in a tank facility known as Circulating Water Channel (CWC) tank was conducted. In the experiment, measurements were performed at 2 (two) different locations which were at the center of propeller and at 0.7R of propeller blade. The results of the research found that the performance of the elliptical intake shape is more optimal compared to the circular one.

Application of a Propeller-Based Air Propulsion System to the Land-Based Holonomic Vehicle

Holonomic vehicles with wheels such as ball wheels can move in any direction without rotating. For such a system, more driving motors and precise transmission mechanisms are necessary, which makes the control and fabrication complicated. This paper aims to present the design and construction of a novel holonomic mechanism to simplify the system. Air-based propulsion was applied to a land-based holonomic vehicle. A prototype with three roller balls was developed with a propeller for the propulsion of a triangular holonomic vehicle. Only two motors were applied, one for propeller rotation and the other for the adjustment of the angle of thrust. For the establishment of the methodology, the data, including propeller size, rotation per minute, velocity, thrust, efficiency, etc., were measured or calculated. The prototype can move at a velocity of approximate 0.558 m/s with an efficiency of 18.55%. Simulation results showed that with the increase of propulsion efficiency, the velocity can achieve more than 5 m/s if the efficiency is 70%. This study is the first attempt to apply air-based propulsion to a land-based holonomic vehicle. Further, the construction method is simple and can satisfy the accuracy requirement. This design method, therefore, will contribute to the application of holonomic vehicles due to the realization of holonomic functionality and simplicity.

An Investigation of the Aerodynamic Performance for a Fuel Saving Double Channel Wing Configuration

This paper presents a fuel saving double channel wing (FADCW) configuration for a propeller driven aircraft to reduce fuel consumption. In pursuit of this objective, FADCW configuration combines the tractor propeller layout and over-the-wing propeller layout. The basic idea is to improve the wing lift-to-drag ratio by taking advantage of the beneficial propeller influence on the wing. Based on a multi reference frame method solving Reynolds averaged Navier-Stokes equations, the contrastive study of this configuration and a traditional tractor propeller-wing layout is conducted. It is shown that the propeller slipstream in the tractor propeller configuration leads to a 10.28% reduction in the wing lift-to-drag ratio. With the same reference wing area and the propeller rotation speed; however, the FADCW configuration can reduce the wing drag by 10.41% and increase its lift-to-drag ratio by 13.29%, which results in a 20.15% reduction in the fuel consumption compared with the traditional tractor propeller configuration.

THE EFFECT OF LEEWAY ANGLE ON THE PROPELLER PERFORMANCE

One of the aspects influencing the performance of wind assisted vessels is the effect of leeway (drift) angle on the propeller performance. It is known that due to leeway the delivered propeller power and propulsive efficiency can vary significantly from the straight sailing condition. This effect of leeway angle is studied using a combination of viscous flow calculations and captive model tests for one twin screw and three single screw vessels. It is observed that the changes in mean axial velocity and pre-swirl rotation in the wakefield due to a combination of leeway angle and propeller suction are sufficient to describe the trends observed in captive model tests. This knowledge is used in a proposed prediction method to model the changes in propeller thrust and torque due to leeway angle at the design stage. The prediction model combined with a fit of the average wake parameters for the studied vessel types is finally used the show the trends in propulsive efficiency and delivered propeller power at constant propeller rotation rate and ship speed for small leeway angles.

Hydrodynamic Analysis and Structural Optimization of an Underwater Robot

BYSQ-2 is an amphibious spherical exploring robot which can move flexibly in water and on land, it has good water pressure resistance and can perform a rotational motion with a zero degree turn radius. But the actual experiment results show the shortcoming of the robot is the low maximum surge speed. The main objective in this paper is to improve the maximum surge speed and alleviate the heavy pendulum’s oscillation. Firstly, the hydrodynamic coupling under different structural parameters and propeller working states is analyzed by using CFD method, the influence of structure parameters and propeller rotation speed on thrust and water resistance are summarized, based on the optimal structural parameters, the new generation robot with better performance is designed. The simulation and experiment results show the validity of the new design scheme.

Numerical simulations of cavitating turbulent flow around a marine propeller behind the hull with analyses of the vorticity distribution and particle tracks

The k-ω SST turbulence model was coupled with a homogenous cavitation model to simulate cavitating turbulent flow around a highly-skewed propeller behind a ship hull. The influence of the mesh resolution was investigated by an uncertainty analysis and comparisons with experimental data. The main contribution in this paper is to study the cavitating flow around the propeller behind the hull by the relative vorticity transport equation and particle trajectories. The results show that the present method can accurately simulate the transient cavitating flow around a marine propeller behind a hull. The predicted thrust coefficients, cavitation patterns and pressure fluctuations agree well with experimental data. Furthermore, the relative vorticity transport equation was used to analyze the cavitation influence on the vorticity transport. These results show that the leading edge vortex, mass transfer across the liquid-vapor interface and the side-entrant jet significantly influence the relative vorticity distribution. Moreover, particle trajectories were predicted using a three-dimensional Lagrangian technology to study the local cavitating flow structure from the Lagrangian viewpoint. The particle tracks demonstrate that the propeller rotation and the twisted geometry lead to a much more complex, distorted flow structures.

Resistance performance simulation of remotely operated vehicle in deep sea considering propeller rotation

In order to predict the resistance performance and movement stability of deep-sea remotely operated vehicle quickly and accurately, the steady-state Reynolds-averaged Navier–Stokes method is used to simulate the force of open-frame remotely operated vehicle with propeller in motion. Volume force model is adopted to simulate the interaction between the propeller and the remotely operated vehicle, solving the force of remotely operated vehicle under the continuous work of two or four screw propellers in the horizontal and vertical motion, as well as the propeller thrust and shaft torque. In addition, according to the simulation result, the shaft torque of the symmetrical distributed propeller is almost equal, so it will not affect the movement stability of remotely operated vehicle. Since no experimental results of these drags and torques have not been performed in this study, it is important to validate the computational fluid dynamics methodology with experimental data and associated motion phenomena by means of numerical simulation. This is the preliminary design stage where extensive hydrodynamic test facilities are not available.

Application of savonius turbine behind the propeller as energy source of fishing vessel in indonesia

The energy wasted by the propeller of vessel can be gained as benefit by converting it using turbine as the source of electrical energy. The electrical energy can be used as the main energy source of fisherman vessel. The method in this research is redesigning the fisherman vessel combined with savonius turbine to obtain the correct dimension. Vessel dimension is built within Loa = 30.71 m; B = 7.67 m; H = 3.5 m; T = 2.2 m. From those dimensions can be obtained the coefficient between the propeller into the pitch 0.8 m, with the turbine diameter 0.5 m and the position of the turbine 0.1 m from the propeller. Savonius turbine captures electrical energy that produced by the low fluid flow that comes out from the propeller rotation, and will be converted by the generator inside the turbine to become energy. The power produced by the rotation of 1.31 rpm of the turbine is 25.689 kilowatt. It is enough to supply the engine generator with the power of 20.1 kilowatt from the power that produced by the turbine as big as 25.689 kilowatt to lighting the fisherman vessel. This technology can be applied massively to the fishermen vessel as renewable energy.

Considerations upon the performances of the main naval engine and energy efficiency evaluation

Nowadays, the essential source of ship propulsion is the diesel low-speed engine, and the power necessity and rate of propeller rotation especially rely upon the ship’s structure and the propeller geometry. Along these lines, in order to arrive at a solution that is as ideal as could be allowed, some broad information is basic for ship diesel engine parameters that impact the propulsion ship system. The performance of any system on board ship is specifically identified with its reliability. So as to get the best out of marine motors, it is critical to screen their performances and take measures to accomplish productive combustion. The paper points the significance of estimating the performances of the propulsion motor utilizing the NHX program. NHX electronic program estimates the pressure inside engine cylinders by the usage of the beat signal from Top Dead Center (T.D.C.) of the number 1 cylinder. Additionally, analyses the after burning period at the combustion stroke of each cylinder. The E.E.O.I. (Energy Efficiency Operational Indicator) is an observing tool for ship management and fleet efficiency. The estimations of the factors have a diminishing trend amid the usage time periods, achieving at least a 30% decrease of the pollutants in the years 2025 contrasted with the values before the implementation of this index. E.E.D.I. index has been considered as the biggest and most dominant sections of the sea business.

The Notched Stick, an ancient vibrot example.

An intriguing simple toy, commonly known as the Notched Stick, is discussed as an example of a “vibrot”, a device designed and built to yield conversion of mechanical vibrations into a rotational motion. The toy, that can be briefly described as a propeller fixed on a stick by means of a nail and free to rotate around it, is investigated from both an experimental and a numerical point of view, under various conditions and settings, to investigate the basic working principles of the device.The conversion efficiency from vibration to rotational motion turns out to be very small, or even not detectable at all, whenever the propeller is tightly connected to the stick nail and perfectly axisymmetrical with respect to the nail axis; the small effects possibly observed can be ascribed to friction forces. In contrast, the device succeeds in converting vibrations into rotations when the propeller center of mass is not aligned with the nail axis, a condition occurring when either the nail-propeller coupling is not tight or the propeller is not completely axisymmetrical relative to the nail axis. The propeller rotation may be induced by a process of parametric resonance for purely vertical oscillations of the nail, by ordinary resonance if the nail only oscillates horizontally or, finally, by a combination of both processes when nail oscillations take place in an intermediate direction. Parametric resonance explains the onset of rotations also when the weight of the propeller is negligible. In contrast with what is commonly claimed in the literature, the possible elliptical motion of the nail, due to a composition of two harmonic motions of the same frequency imposed along orthogonal directions, seems unnecessary to determine the propeller rotation.

РАСЧЕТ МОЩНОСТИ ДВУНАПРАВЛЕННОГО ПРЕОБРАЗОВАТЕЛЯ ПОСТОЯННОГО НАПРЯЖЕНИЯ АВТОНОМНЫХ ПОДВОДНЫХ АППАРАТОВ

One of the ways to increase the efficiency of autonomous underwater vehicles is to use a DC electric power system. With the help of impulse control it is possible to achieve a stable voltage on consumers even with significant changes in the speed of the propeller rotation caused by waves, bottom relief, current, winds, course change, etc. Issues related to the simulation of DC-DC converters for autonomous underwater vehicles have been considered. The powers supplied from a DC power source to loading have been found. Possible ways of regulating the power and voltage at the output of the pre-driver are analyzed and performing the power and voltage adjustment by means of the phase angle to the inverting and rectifying bridges is proved to be expedient. At an angle of 90º, the current in the pulse transformer looks like a sinusoid in shape, and at the same time it is simple for piecewise linear approximation, which in turn makes it easy to determine the transmitted power over a period. Various variants of an output signal are presented under changing a phase angle of opening of IGBT-transistors. There have been illustrated oscillograms of the AC-DC converter and of the current type in the inductor. According to the calculations, the analytical solution was found to determine the transmitted power. A bi-directional DC converter was modeled using a Simulink package, which resulted in a voltage on the inductor and voltage on the load as a graphic dependence. The obtained dependences completely coincide with the theoretical analysis.