Experimental investigation of blade and propeller loads: Steady turning motion     

《Applied Ocean Research》2019

This paper is the continuation of the work described in [14], dedicated to the presentation of the results of propeller performance in behind-hull during straight ahead motion obtained by a novel experimental set-up for the measurements of single blade loads. In the present case, the study shows and discusses the single blade and propeller loads developed during steady turning conditions, that were simulated by means of free running, self propelled maneuvering tests for a twin screw configuration. Maneuvering conditions are critical for the ship propulsion system, because the performance of the propeller and the side effects related to its functioning (propeller–hull induced pressure and vibrations, noise) are completely different with respect to the design condition in straight ahead motion. Thrust and torque and generation of in-plane loads (force and moments), developed by the blade during the period, evolve differently for the two propellers, due to different propeller–wake interactions. The understanding and the accurate quantification of propeller loads, in these realistic operative scenarios, are pivotal to design low emission and comfortable ships, fulfilling the requirements of safety and continuity of operations at sea. The analysis is carried out revisiting the investigation in [14] for three different speeds (F_N = 0.26, 0.34 and 0.40) and a large set of rudder angles that span moderate and tight maneuvers.  相似文献   

Effect of various winglets on the performance of marine propeller     

《Applied Ocean Research》2019

The tip vortex cavitation (TVC) is an issue of increasing interest, because the TVC plays an important role in propeller radiated noise and cavitation erosion. The marine propeller with winglets, which is inspired by the winglets of airfoil, is numerically investigated in the present paper. The blade tip of newly designed propeller tilts toward the pressure side. The difference between six propellers is the change of the rake angle at r/R = 1.0. The pressure coefficient, TVC, axial velocity field and helicity are analyzed. The numerical results show that the winglets of newly designed propeller scarcely affect the efficiency of propeller. The thrust coefficient gradually decreases with the increase in rake angle. As for the suction side, the pressure coefficient (C_p) of winglets propellers is higher than the conventional propeller in general. In addition, the winglets are beneficial to generate less cavitation behavior when the rake angle is small. However, as the rake angle is further increased, the cavitation behavior of winglets propeller is also increased, even larger than the conventional propeller. Therefore, it can be deduced that the winglets can be used to effectively improve the TVC characteristics to some extent.  相似文献   

降雨强度对激光雷达测风精度的影响研究     

陈泉  史文浩  汤杰  赵兵科  陈叙捷  陈勇航  林立旻  严嘉明  马骁骏  骆梦洁 《气象科技》2022,50(3):324-333

多普勒激光雷达在大气、环境以及风能等领域得到越来越广泛的应用,但对于复杂天气下多普勒激光雷达的适用性仍然有待深入研究。为此本研究采用2020年8—10月期间位于福建三沙的地基多普勒激光雷达与边界层高塔所搭载的超声风温仪观测的风场数据进行对比,发现多普勒激光雷达在水平风速、风向方面具有稳定的高精度探测性能,与超声风温仪之间相关系数达到了0.948和0.984。相比之下,激光雷达垂直风速的探测误差较大,与超声风温仪之间相关系数仅有0.353。研究发现,降雨强度与激光雷达垂直风速误差呈正相关关系,强降雨下垂直风速偏差最大可达到9 m/s。  相似文献   

Estimating the turbulent energy dissipation rate in an airport environment     

Michael Frech 《Boundary-Layer Meteorology》2007,123(3):385-393

This note reports on the influence of aircraft wake vortices on the estimation of the turbulent energy dissipation rate using sonic anemometer measurements near the runway threshold. The wake vortex traces, which are generated at a height of about 65 m and subsequently evolve in ground effect, are clearly visible in the velocity components and temperature. The observed temperature increase of 1 K appears related to the stably stratified atmospheric surface layer. The dissipation rate is estimated from the longitudinal velocity power spectrum for a sample in a nocturnal boundary layer with and without a wake vortex signal. In both cases an inertial subrange is found. For the analyzed sample the estimated dissipation rate is a factor of ten larger compared to the undisturbed sample. Implications for operational wake avoidance systems are discussed.  相似文献   

Behaviour Of An Ultrasonic Anemometer Under Cloudy Conditions     

Holger Siebert  Ulrich Teichmann 《Boundary-Layer Meteorology》2000,94(1):165-169

The use of ultrasonic anemometers under cloudy weather conditions is often doubted, even rejected or not discussed in the literature. To investigate the influence of liquid water content on the behaviour of sonic anemometers a small intercomparison experiment using an ultrasonic anemometer, a fast response propeller anemometer, and a Particulate Volume Monitor was performed at the German Environmental Research Station Schneefernerhaus near the top of Mt. Zugspitze. The results obtained under different conditions (dry/cloudy) give no significant hint on such an influence.  相似文献   

三维超声风速仪观测中风向角计算方法   总被引：2，自引：0，他引：2  

姜明  景元书  郭建侠  王有恒 《气象科技》2011,39(5):615-619

在对三维超声风速仪观测资料处理中,风向角的计算具有一定的技巧性。根据三维超声风速仪自身观测坐标系统与地理坐标系之间的差异,推导出计算地理坐标系下风向角的一种方法,为超声风观测资料的处理和应用提供借鉴。同时利用锡林浩特国家气候观象台2008年全年通量观测资料对风向角进行了计算,并与台站统计资料进行了对比,结果表明两组数据无论从风向角分布趋势还是从相关性来看,均非常吻合（相关系数为0.97）,从而证明了该方法的正确性及可应用性。  相似文献   

A field study of mean and turbulent flow characteristics upwind,over and downwind of barchan dunes   总被引：1，自引：0，他引：1  

Matthew C. Baddock  Giles F. S. Wiggs  Ian Livingstone 《地球表面变化过程与地形》2011,36(11):1435-1448

Field‐measured patterns of mean velocity and turbulent airflow are reported for isolated barchan dunes. Turbulence was sampled using a high frequency sonic anemometer, deriving near‐surface Reynolds shear and normal stresses. Measurements upwind of and over a crest‐brink separated barchan indicated that shear stress was sustained despite a velocity reduction at the dune toe. The mapped streamline angles and enhanced turbulent intensities suggest the effects of positive streamline curvature are responsible for this maintenance of shear stress. This field evidence supports an existing model for dune morphodynamics based on wind tunnel turbulence measurements. Downwind, the effect of different dune profiles on flow re‐attachment and recovery was apparent. With transverse incident flow, a re‐attachment length between 2·3 and 5·0h (h is dune brink height) existed for a crest‐brink separated dune and 6·5 to 8·6h for a crest‐brink coincident dune. The lee side shear layer produced elevated turbulent stresses immediately downwind of both dunes, and a decrease in turbulence with distance characterized flow recovery. Recovery of mean velocity for the crest‐brink separated dune occurred over a distance 6·5h shorter than the crest‐brink coincident form. As the application of sonic anemometers in aeolian geomorphology is relatively new, there is debate concerning the suitability of processing their data in relation to dune surface and streamline angle. This paper demonstrates the effect on Reynolds stresses of mathematically correcting data to the local streamline over varying dune slope. Where the streamline angle was closely related to the surface (windward slope), time‐averaged shear stress agreed best with previous wind tunnel findings when data were rotated along streamlines. In the close lee, however, the angle of downwardly projected (separated) flow was not aligned with the flat ground surface. Here, shear stress appeared to be underestimated by streamline correction, and corrected shear stress values were less than half of those uncorrected. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

用断裂力学校核带裂纹的船舶螺旋浆轴     

陈贤 《广东海洋大学学报》1990,(2)

本文以实船带裂纹螺旋浆轴为例,应用断裂力学分析方法校核其剩余强度和裂纹扩展速率,判别可用性,然后提出防断裂措施;为断裂力学在船舶机械修理技术中的应用作了一个尝试,补充了船舶机械轴件常规强度校核方法的不足。  相似文献   

Energy coefficients for a propeller series     

Anders Smrup Olsen 《Ocean Engineering》2004,31(3-4):401-416

The efficiency for a propeller is calculated by energy coefficients. These coefficients are related to four types of losses, i.e. the axial, the rotational, the frictional, and the finite blade number loss, and one gain, i.e. the axial gain. The energy coefficients are derived by use of the potential theory with the propeller modelled as an actuator disk. The efficiency based on the energy coefficients is calculated for a propeller series. The results show a good agreement between the efficiency based on the energy coefficients and the efficiency obtained by a vortex-lattice method.  相似文献   

Airflow and aeolian sediment transport patterns within a coastal trough blowout during lateral wind conditions   总被引：5，自引：0，他引：5       下载免费PDF全文

Thomas Andrew George Smyth  Derek Jackson  Andrew Cooper 《地球表面变化过程与地形》2014,39(14):1847-1854

Blowouts are depressions that occur on coastal dunes, deserts and grasslands. The absence of vegetation in blowouts permits high speed winds to entrain and remove sediment. Whereas much research has examined patterns of wind flow and sediment transport on the stoss slopes and lee of sand dunes, no study has yet investigated the connections between secondary air‐flow structures and sediment transport in a blowout where zones of streamline compression, expansion and steering are less clearly delineated. In this study we investigated the variability of sediment flux and its relation to near‐surface wind speed and turbulence within a trough blowout during wind flow that was oblique to the axis of the blowout. Wind flow was measured using six, three‐dimensional (3D) ultrasonic anemometers while sediment flux by eight sand traps, all operating at 25 Hz. Results demonstrated that sediment flux rates were highly variable throughout the blowout deflation basin, even over short distances (< 0.5 m). Where flow was steadiest, flux was greatest. Consequently the highest rates of sediment transport were recorded on the erosional wall crest where flow was compressed and accelerated. The strength of correlation between sediment flux and wind parameter improved with an increase in averaging interval, from 10 seconds to 1 minute. At an interval of 10 seconds, however, wind speed correlated best with flux at seven of eight traps, whereas at an interval of one minute Turbulent Kinetic Energy (TKE) provided the best correlation with flux at six of the eight traps. Correlation between sediment flux and wind parameters was best in the centre of the blowout and poorest on the erosional wall crest. The evidence from this paper suggests, for the first time, that TKE may be a better predictor of sediment transport at minute scale averaging intervals, particularly over landforms where wind flow is highly turbulent. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献