The effects of corrugation and wing planform on the aerodynamic force production of sweeping model insect wings

The effects of corrugation and wing planform （shape and aspect ratio） on the aerodynamic force production of model insect wings in sweeping （rotating after an initial start） motion at Reynolds number 200 and 3500 at angle of attack 40℃ are investigated, using the method of computational fluid dynamics. A representative wing corrugation is considered. Wing-shape and aspect ratio （AR） of ten representative insect wings are considered; they are the wings of fruit fly, cranefly, dronefly, hoverfly, ladybird, bumblebee, honeybee, lacewing （forewing）, hawkmoth and dragon- fly （forewing）, respectively （AR of these wings varies greatly, from 2.84 to 5.45）. The following facts are shown. （1） The corrugated and flat-plate wings produce approximately the same aerodynamic forces. This is because for a sweeping wing at large angle of attack, the length scale of the corrugation is much smaller than the size of the separated flow region or the size of the leading edge vortex （LEV）. （2） The variation in wing shape can have considerable effects on the aerodynamic force; but it has only minor effects on the force coefficients when the velocity at r2 （the radius of the second ：moment of wing area） is used as the reference velocity; i.e. the force coefficients are almost unaffected by the variation in wing shape. （3） The effects of AR are remarkably small： whenAR increases from 2.8 to 5.5, the force coefficients vary only slightly; flowfield results show that when AR is relatively large, the part of the LEV on the outer part of the wings sheds during the sweeping motion. As AR is increased, on one hand, the force coefficients will be increased due to the reduction of 3-dimensional flow effects; on the other hand, they will be decreased due to the shedding of part of the LEV; these two effects approximately cancel each other, resulting in only minor change of the force coefficients.

Reconstruction of meandering paleo-channels using dense well data,Daqing Oil Field,Songliao Basin,China

Reconstructing meandering paleo-channels is attracting global research attention. We implemented a novel method by comprehensively integrating migration models and sedimentary structures. Firstly, the migration architectures of the corresponding characteristics in planform and cross-sectional models were summarised as expansion, translation, expansion and translation, expansion and downstream rotation, constriction and downstream rotation, and expansion and countercurrent rotation models. Secondly, full continuous core data from 270 dense drilling wells were collected from the Daqing Oil Field in the Songliao Basin, China, providing information on rock textures, sedimentary cycles, and boundary information for the two layers being studied. Through a comprehensive analysis of dense drill cores and logging data, the abandoned channels and the initial and final channel centrelines were identified. Consequently, four profiles, including one longitudinal and three transverse sections, were constructed to reveal the cross-sectional structures and planform migration architecture. Profile interpretation revealed the evolution from the initial channel centreline to the final centreline. Using a method of rational interpolation, we were able to reconstruct the migration architecture of the meandering channels. The results showed that the average ancient bankfull width(Wc) was approximately 100 m, a single meandering belt was800 m, the radius of the curvature was 250 m, the length of the channel bend was 700 m, the average meander wavelength was 1300 m, the sinuosity was 3.0, and the annual average discharge rate was 450 m3/s. Furthermore, we compared the results from empirical equations, which verified that our reconstruction is both feasible and potentially widely applicable.

Geomorphology Processes of Channel Planform Migration on Meandering Rivers

1 Introduction Morphological analysis on the planform migration structure of meandering river is an important basis for the reconstruction of evolution of paleochannel.Besides,it is a significant method for restoration of rivers through the

Simulating Long Waves in a Coifs Harbour 3D Physical Model Using Short Wave Spectra

This paper presents examples of field data of extreme seiche waves measured at Coffs Harbour by MHL and describes the generation and measuring methodology to detect and reduce seiche agitation in the Coifs Harbour boat ramp using a 3D physical model. The paper also discusses the techniques in investigating a short wave problem of stability in the same model where a long wave is simulated. Waves offshore of Coffs Harbour at 80 m depth have been recorded by MHL for a period of over 30 years. Long waves have been simultaneously measured in the harbour over a period of a decade. These data enabled the model to be verified on two dates （4/6/12, 5/9/14） when high long waves were recorded at the boat ramp harbour under storm and non-storm conditions. Long waves are generated in harbours due to group bounded long wave and surf beat or edge waves. The paper presents methodologies of generating long waves both numerically and by using physical models, and discusses the advantages and disadvantages of these generation techniques. Numerical modelling carried out using long period regular waves in a previous investigation predicted reductions up to 50% due to change of planform of the boat ramp harbour where an area next to the boat ramp was excavated and roughness elements introduced to dampen long periods. The 3D physical model simulated a 25% decrease in the long wave energy in the boat ramp when a suitable change in the planform was made. A 3D undistorted model of scale 1：58 was used in the investigation.

Aerodynamic design optimization of helicopter rotor blades including airfoil shape for hover performance

This study proposes a process to obtain an optimal helicopter rotor blade shape for aerodynamic performance in hover flight. A new geometry representation algorithm which uses the class function/shape function transformation （CST） is employed to generate airfoil coordinates. With this approach, airfoil shape is considered in terms of design variables. The optimization process is constructed by integrating several programs developed by author. The design variables include twist, taper ratio, point of taper initiation, blade root chord, and coefficients of the airfoil distribution function. Aerodynamic constraints consist of limits on power available in hover and forward flight. The trim condition must be attainable. This paper considers rotor blade configuration for the hover flight condition only, so that the required power in hover is chosen as the objective function of the optimization problem. Sensitivity analysis of each design variable shows that airfoil shape has an important role in rotor performance. The optimum rotor blade reduces the required hover power by 7.4% and increases the figure of merit by 6.5%, which is a good improvement for rotor blade design.

Planform characteristics and development of inter- channel wetlands in a gravel-bed anastomosing river, Maqu Reach of the Upper Yellow River

Both interchannel wetlands and multi-channels are crucial geomorphologic units in an anastomosing river system. Planform characteristics and development of interchannel wetlands and multi-channels control the characteristics of anastomosing rivers. To under- stand the role that interchannel wetlands play in the development of anastomosing rivers, a study was conducted on the Maqu Reach of the Upper Yellow River （MRUYR）, a gravel-bed anastomosing river characterized by highly developed interchannel wetlands and ana- branches. Geomorphologic units in the studied reach were extracted from high resolution satellite imagery in Google Earth. The size distributions of interchannel wetlands and inter- channel wetland clusters （IWCs）, a special combination of interchannel wetlands and ana- branches, were investigated. Geomorphologic parameters, including the ratio of interchannel wetland area to IWC area （P）, shoreline density （DL）, and node density （Dn） were used to analyze planform characteristics of IWCs and the development of multi-channels in the stud- ied reach. The results suggest that small or middle sized interchannel wetlands and large or mega sized IWCs are more common at the study site. The area of IWC （Su） is highly cor- related with other geomorphologic parameters. P increases with increasing Su, and the upper limit is about 80%, which indicates that the development of interchannel wetlands and ana- branches in the IWC is in the equilibrium stage. In contrast, D~ and D, show a tendency to decrease with increasing Su due to diverse evolution processes in IWCs with different sizes. There are three main reasons leading to the formation of IWCs： varying stream power due to the meandering principal channel; development of the river corridor due to the weakening of geologic structure control; and high stability of interchannel wetlands due to conservation by shoreline vegetation.

Lateral erosion/accretion area and shrinkage rate of the Linhe reach braided channel of the Yellow River between 1977 and 2014

Quantitative studies on river channel lateral erosion/accretion area changes over time can reveal the characteristics of channel evolution. Taking the 213-km-long Linhe reach braided channel of the Yellow River as an example, area changes in channel bank ero- sion/accretion in four sub-reaches （S1, S2, S3 and S4） over 19 different periods were evalu- ated on the basis of remote sensing images captured since 1977. Mean channel shrinkage rate for the whole river reach was also obtained. Results show that the left and right banks of the Linhe reach were dominated by lateral net accretion between 1977 and 2014. The channel area of this section of the Yellow River was characterized by reduction between 1977 and 2001, while periods of alternate erosion and accretion occurred subsequent to 2001. Mean channel shrinkage rate in the Linhe reach braided channel was 6.15 km2/yr between 1977 and 2014, while the most remarkable changes in channel planform occurred in the 1990s. Compared to 1995, channel length and sinuosity increased by 5.8% and 6.6% by 2000, while channel area and mean width decreased by 39.4% and 42.8%, respectively. Significant changes in channel planform and shrinkage of the Linhe reach occurred in the 1990s, mainly as a result of the joint-operation of the Longyangxia and Liujiaxia reservoirs since 1986, which caused substantial reductions in runoff and sediment flux during the annual flooding season. In addition, bank erosion/accretion in the four sub-reaches was affected by the physical properties of local banks, engineering emplaced to protect channel banks, and hydrodynamic differences. However, since the implementation of integrated river manage- ment measures from 2000 onwards, these changes have been significantly mitigated and the health of the Linhe reach braided channel of the Yellow River has been restored.

Design methodology of an osculating cone waverider with adjustable sweep and dihedral angles

When considering the practical engineering application of a waverider,the on-design and off-design aerodynamic characteristics of the design conditions,especially the lift-to-drag ratio and the stability,deserve attention.According to recently studies,the planform and rear sight shape of a waverider are closely related to the above aerodynamic performance.Thus,the planform leading-edge profile curve used to design the planform shape of a vehicle is applied to designing an osculating cone waverider.Two key parameters concerned in planform and rear sight shape,namely the plan view sweep angle of the leading edge and the dihedral angle of the underside are introduced to the waverider design process.Each parameter is inserted in the control curve equation.Especially,a parameterization scheme is put forward for the free adjustment of the sweep angle along the leading edge.Finally,three examples are generated for verification and investigation.After the verification process based on the inviscid flow field of one case,the influences of the sweep and dihedral angles on the lift-to-drag ratio and the lateral static stability are evaluated,and meaningful results are obtained.Based on these results,we can conclude that,considering the maximum lift-to-drag ratio,the sweep angle plays a role on the lift-to-drag ratio only at subsonic and trans/supersonic speed as a negligible effect is observed at hypersonic speeds,whereas the dihedral angle is seem to produce a relevant difference at hypersonic speeds.Considering the lateral static stability,the dihedral angles have more influence on the waverider than the sweep angles.