A Phased Aerodynamic Optimization Method for Compressors Based on Multi-Degrees-of-Freedom Surface Parameterization

High-fidelity aerodynamic optimization of compressors is afflicted by the"curse of dimensionality",which limits its engineering applications.This paper proposes a new multi-degrees-of-freedom(MDOF)surface parameterization method that combines the characteristics of conventional surface parameterization methods,low-dimensionality and surface smoothness,with the advantages of design flexibility and ease of construction.The proposed method is applied to the high-fidelity aerodynamic optimization of Rotor37.An optimized solution is obtained within 111 h by combining a phased optimization strategy based on the idea of modal optimization.To explore a better way of setting the control variables of the blade body,two methods of varying the control points of the suction and pressure surfaces,independent change and synchronous change,are compared.Synchronous change has better flexibility,and under the condition of satisfying the constraints,it increases the efficiency at the design point by 2.2%and the surge margin by 0.5%.This demonstrates the effectiveness of the proposed method in the high-fidelity aerodynamic optimization of compressors.It also provides technical support to solve the"curse of dimensionality"problem.

Effects of Surface Flux Parameterization on the Numerically Simulated Intensity and Structure of Typhoon Morakot(2009)

The effects of surface flux parameterizations on tropical cyclone（TC） intensity and structure are investigated using the Advanced Research Weather Research and Forecasting（WRF-ARW） modeling system with high-resolution simulations of Typhoon Morakot（2009）.Numerical experiments are designed to simulate Typhoon Morakot（2009） with different formulations of surface exchange coefficients for enthalpy（C_K） and momentum（C_D） transfers,including those from recent observational studies based on in situ aircraft data collected in Atlantic hurricanes.The results show that the simulated intensity and structure are sensitive to C_K and C_D,but the simulated track is not.Consistent with previous studies,the simulated storm intensity is found to be more sensitive to the ratio of C_K/C_D than to C_K or C_D alone.The pressure-wind relationship is also found to be influenced by the exchange coefficients,consistent with recent numerical studies.This paper emphasizes the importance of C_D and C_K on TC structure simulations.The results suggest that C_D and C_K have a large impact on surface wind and flux distributions,boundary layer heights,the warm core,and precipitation.Compared to available observations,the experiment with observed C_D and C_K generally simulated better intensity and structure than the other experiments,especially over the ocean.The reasons for the structural differences among the experiments with different C_D and C_K setups are discussed in the context of TC dynamics and thermodynamics.

Influence of Minimum Quantity Lubrication Parameters on Tool Wear and Surface Roughness in Milling of Forged Steel

The minimum quantity of lubrication（MQL） technique is becoming increasingly more popular due to the safety of environment.Moreover,MQL technique not only leads to economical benefits by way of saving lubricant costs but also presents better machinability.However,the effect of MQL parameters on machining is still not clear,which needs to be overcome.In this paper,the effect of different modes of lubrication,i.e.,conventional way using flushing,dry cutting and using the minimum quantity lubrication（MQL） technique on the machinability in end milling of a forged steel（50CrMnMo）,is investigated.The influence of MQL parameters on tool wear and surface roughness is also discussed.MQL parameters include nozzle direction in relation to feed direction,nozzle elevation angle,distance from the nozzle tip to the cutting zone,lubricant flow rate and air pressure.The investigation results show that MQL technique lowers the tool wear and surface roughness values compared with that of conventional flood cutting fluid supply and dry cutting conditions.Based on the investigations of chip morphology and color,MQL technique reduces the cutting temperature to some extent.The relative nozzle-feed position at 120°,the angle elevation of 60° and distance from nozzle tip to cutting zone at 20 mm provide the prolonged tool life and reduced surface roughness values.This fact is due to the oil mists can penetrate in the inner zones of the tool edges in a very efficient way.Improvement in tool life and surface finish could be achieved utilizing higher oil flow rate and higher compressed air pressure.Moreover,oil flow rate increased from 43.8 mL？h to 58.4 mL？h leads to a small decrease of flank wear,but it is not very significant.The results obtained in this paper can be used to determine optimal conditions for milling of forged steel under MQL conditions.

Optimization of Inactivation Conditions of High Hydrostatic Pressure Using Response Surface Methodology

Response surface methodology (RSM) was employed in the present work and a second orderquadratic equation for high hydrostatic pressure (HHP) inactivation was built. Theadequacy of the model equation for predicting the optimum response values was verifiedeffectively by the validation data. Effects of temperature, pressure, and pressureholding time on HHP inactivation of Escherichia coli ATCC 8739 were explored. Byanalyzing the response surface plots and their corresponding contour plots as well assolving the quadratic equation, the optimum process parameters for inactivation E. coliof six log cycles were obtained as: temperature 32.2℃, pressure 346.4 MPa, and pressureholding time 12.6min.

SURFACE EXCITATION PARAMETER IN QUANTITATIVE SURFACE ANALYSIS BY ELECTRON SPECTROSCOPY

The investigation of influence of surface effects on the energy spectra of elect rons is essential for comprehensive understanding of electron-solid interactions as well as quantitative analysis. The accuracy of the analysis depends on the m odels for elastic and inelastic interactions. Electrons impinging on a solid or escaping from it suffer losses in the surface layer. The energy loss spectra the refore have contributions from surface excitations. The role of surface excitati ons is characterized by surface excitation parameter (SEP), which indicates the number of surface plasmons created by an electron crossing the surface. The imag inary part of complex self-energy of an electron is related to the energy loss c ross section. SEP is numerically computed using self-energy formalism and compar ed with the results as described and calculated by different workers.

Characterization of surface damage of a solid plate under tensile loading using nonlinear Rayleigh waves

This letter reports experimental observation of a direct correlation between the acoustic nonlinearity parameter (NP) measured with nonlinear Rayleigh waves and the accumulation of plasticity damage in an AZ31 magnesium alloy plate specimen.Rayleigh waves are generated and detected with wedge transducers,and the NPs are measured at different stress levels.The results show that there is a significant increase in the NPs with monotonic tensile loads surpassing the material’s yielding stress.The research suggests an effective nondestructive evaluation method to track the surface damage in metals.

The Characteristics and Controlling Factors of Water and Heat Exchanges over the Alpine Wetland in the East of the Qinghai–Tibet Plateau

Alpine wetland is one of the typical underlying surfaces on the Qinghai–Tibet Plateau.It plays a crucial role in runoff regulation.Investigations on the mechanisms of water and heat exchanges are necessary to understand the land surface processes over the alpine wetland.This study explores the characteristics of hydro-meteorological factors with in situ observations and uses the Community Land Model 5 to identify the main factors controlling water and heat exchanges.Latent heat flux and thermal roughness length were found to be greater in the warm season(June–August)than in the cold season(December–February),with a frozen depth of 20–40 cm over the alpine wetland.The transfers of heat fluxes were mainly controlled by longwave radiation and air temperature and affected by root distribution.Air pressure and stomatal conductance were also important to latent heat flux,and soil solid water content was important to sensible heat flux.Soil temperature was dominated by longwave radiation and air temperature,with crucial surface parameters of initial soil liquid water content and total water content.The atmospheric control factors transitioned to precipitation and air temperature for soil moisture,especially at the shallow layer(5 cm).Meanwhile,the more influential surface parameters were root distribution and stomatal conductance in the warm season and initial soil liquid water content and total water content in the cold season.This work contributes to the research on the land surface processes over the alpine wetland and is helpful to wetland protection.

Area-Preserving Parameterization with Tutte Regularization

Area-preserving parameterization is now widely applied,such as for remeshing and medical image processing.We propose an efficient and stable approach to compute area-preserving parameterization on simply connected open surfaces.From an initial parameterization,we construct an objective function of energy.This consists of an area distortion measure and a new regularization,termed as the Tutte regularization,combined into an optimization problem with sliding boundary constraints.The original area-preserving problem is decomposed into a series of subproblems to linearize the boundary constraints.We design an iteration framework based on the augmented Lagrange method to solve each linear constrained subproblem.Our method generates a high-quality parameterization with area-preserving on facets.The experimental results demonstrate the efficacy of the designed framework and the Tutte regularization for achieving a fine parameterization.

Parameterization of land surface albedo

Remote measurements of Earth’s surface from ground, airborne, and spaceborne instruments show that its albedo is highly variable and is sensitive to solar zenith angle（SZA） and atmospheric opacity. Using a validated radiative transfer calculating toolbox, DISORT and a bidirectional reflectance distribution function library, AMBRALS, a land surface albedo（LSA） lookup table（LUT） is produced with respect to SZA and aerosol optical depth. With the LUT, spectral and broadband LSA can be obtained at any given illumination geometries and atmospheric conditions. It provides a fast and accurate way to simulate surface reflectance over large temporal and spatial scales for climate study.

SENSITIVITY TESTS OF INTERACTION BETWEEN LAND SURFACE PHYSICAL PROCESS AND ATMOSPHERIC BOUNDARY LAYER

In this paper,an interactive model between land surface physical process and atmosphere boundary layer is established,and is used to simulate the features of soil environmental physics, surface heat fluxes,evaporation from soil and evapotranspiration from vegetation and structures of atmosphere boundary layer over grassland underlying.The sensitivity experiments are engaged in primary physics parameters.The results show that this model can obtain reasonable simulation for diurnal variations of heat balance,soil volumetric water content,resistance of vegetation evaporation,flux of surface moisture,and profiles of turbulent exchange coefficient,turbulent momentum,potential temperature,and specific humidity.The model developed can be used to study the interaction between land surface processes and atmospheric boundary layer in city regions,and can also be used in the simulation of regional climate incorporating a mesoscale model.

Nonlinear Adaptive Robust Control Design for Static Synchronous Compensator Based on Improved Dynamic Surface Method

In view of single machine to infinite bus system with static synchronous compensator, which is affected by internal and external disturbances, a nonlinear adaptive robust controller is constructed based on the improved dynamic surface control method(IDSC). Compared with the conventional DSC, the sliding mode control is introduced to the dynamic surface design procedure, and the parameter update laws are designed using the uncertainty equivalence criterions. The IDSC method not only reduces the complexity of the controller but also greatly improves the system robustness, speed and accuracy. The derived controller cannot only attenuate the influences of external disturbances against system output, but also has strong robustness to system parameters variance because the damping coefficient is considered in the internal parameter uncertainty. Simulation result reveals that the designed controller can effectively improve the dynamic performances of the power system.

OPTIMIZATION OF A WAVE CANCELLATION MULTIHULL SHIP USING CFD TOOLS

A simple CFD tool, coupled to a discrete surface representation and a gradient based optimization procedure, is applied to the design of optimal hull forms and optimal arrangement of hulls for a wave cancellation multihull ship. The CFD tool, which is used to estimate the wave drag, is based on the zeroth order slender ship approximation. The hu ll surface is represented by a triangulation, and almost every grid point on the surface can be used as a design variable. A smooth surface is obtained via a si mplified pseudo shell problem. The optimal design process consists of two steps . The optimal center and outer hull forms are determined independently in the fi rst step, where each hull forms are determined independently in the first step, where each hull keeps the same displacement as the original design while the wav e drag is minimized. The optimal outer hull arrangement is determined in the se cond step for the optimal center and outer hull forms obtained in the first step . Results indicate that the new design can achieve a large wave drag reduction i n comparison to the original design configuration.