A copy of Guangbo jiemu bao [Broadcast Program Report] was being passed from hand to hand among a group of young people eager to be the first to read the article introducing the program "What Is Revolutionary Love?" It said: "… Young friends, you are certainly very concerned about this problem'. So, we would like you to meet the young women workers Meng Xiaoyu and Meng Yamei and the older cadre Miss Feng. They are the three leading characters in the short story ‘The Place of Love.’ Through the description of the love lives of these three, the story induces us to think deeply about two questions that merit further examination.

This is How the Discussion Started

Natural ventilation of buildings is the flow generated by temperature differences and by the wind. The governing feature of this flow is the exchange between an interior space and the external ambient. Although the wind may often appear to be the dominant driving mechanism, in many circumstances temperature variations play a controlling feature on the ventilation since the directional buoyancy force has a large influence on the flow patterns within the space and on the nature of the exchange with the outside. Two forms of ventilation are discussed: mixing ventilation, in which the interior is at an approximately uniform temperature, and displacement ventilation, where there is strong internal stratification. The dynamics of these buoyancy-driven flows are considered, and the effects of wind on them are examined. The aim behind this work is to give designers rules and intuition on how air moves within a building; the research reveals a fascinating branch of fluid mechanics.

The fluid mechanics of natural ventilation

Voids, the most studied type of manufacturing defects, form very often in processing of fiber-reinforced composites. Due to their considerable influence on physical and thermomechanical properties ...

https://journals.sagepub.com/doi/pdf/10.1177/0021998318772152

Voids in fiber-reinforced polymer composites: A review on their formation, characteristics, and effects on mechanical performance:

流体力学用語集 非線形音響学(Nonlinear acoustics)

The study of rotor blade aerodynamic performances of wind turbine has been presented in this thesis. This study was focused on aerodynamic effects changed by blade surface distribution as well as grid solution along the airfoil. The details of numerical calculation from Fluent were described to help predict accurate blade performance for comparison and discussion with available data. The direct surface curvature distribution blade design method for two-dimensional airfoil sections for wind turbine rotors have been discussed with the attentions to Euler equation, velocity diagram and the factors which affect wind turbine performance and applied to design a blade geometry close to an existing wind turbine blade, Eppler387, in order to argue that the blade surface drawn by direct surface curvature distribution blade design method contributes aerodynamic efficiency. The FLUENT calculation of NACA63-215V showed that the aerodynamic characteristics agreed well with the available experimental data at lower angles of attack although it was discontinuities in the surface curvature distributions between 0.7 and 0.8 in x/c. The discontinuities were so small that the blade performance could not be affected. The design of Eppler 387 blade performed to reduce drag force. The discontinuities of surface distribution matched the curve of the pressure coefficients. It was found in the curvature distribution that the leading edge pressure side had difficulties to connect to Bezier curve and also the trailing edge circle was never be tangent to the lines of trailing edge pressure and suction sides due to programming difficulties.

Aerodynamics of wind turbines

https://cronfa.swan.ac.uk/Record/cronfa38902/Download/0038902-30042018093722.pdf

Experimental investigation of the flow past passive vortex generators on an airfoil experiencing three-dimensional separation

The present paper is the second part of a combined (experimental and computational) study on stall cells (SCs) on a rectangular wing. In the first part, tuft data were used in order to geometrically characterize a stabilized SC resulting from a localized spanwise disturbance introduced by a zigzag tape. Here, pressure measurements on the model and in the wake and aerodynamic polars at midspan are reported. The wing model had an aspect ratio value of 2, the Reynolds number was 106 and the range of angles of attack (α) was from −6° to 16°. Experimental results confirm previous findings. Furthermore, two-dimensional and three-dimensional Reynolds Averaged Navier-Stokes RANS simulations are used in order to better understand the structure of SCs. 3D simulations reproduce the experimental data with a 3° delay in α and permit a qualitative analysis. It is found that the SC vortices start normal to the wing surface and extend downstream in the wake; the evolution of the SC vortices in the wake is in strong interaction with the separation line vortex and the trailing edge line vortex; as the SC vortex develops downstream in the wake, its centreline is contracted towards the SC centre; the wing wake is pushed upstream at the centre of the SC and downstream at the sides by the SC vortices; spanwise lift and drag distributions always attain their minimum at the SC centre. Copyright © 2013 John Wiley & Sons, Ltd.

/pdf/experimental-and-computational-analysis-of-stall-cells-on-5cvxdcdypv.pdf

Experimental and computational analysis of stall cells on rectangular wings

The present study reports about the pultrusion of a carbon fiber- reinforced PA12 yarn containing discontinuous carbon and polyamide fibers. This is the first attempt to pultrude this material. Rectangular cross sectional profiles have been successfully produced using a self-designed pultrusion line. In a series of experiments, the pultrusion parameters, such as preheating method, die temperature, and especially the pulling speed, which represents a determining factor regarding a potential industrial application, are varied. A complete characterization of each profile is conducted to examine the influence of processing parameters on the profile quality. The mechanical properties are evaluated by performing three-point bending as well as shear tests. The void content is also determined. The pulling speed seems to have the greatest influence on the profile quality. Under certain conditions of speed and temperature, the pultruded profiles exhibit good mechanical performance and a void content below 2%. The shear strength reacts most sensitively to the process parameter variations and can be used as a quality criteria.

/pdf/an-experimental-study-of-the-pultrusion-of-carbon-fiber-5dhg8dott6.pdf

An Experimental Study of the Pultrusion of Carbon Fiber-Polyamide 12 Yarn

The structure of Stall Cells (SCs) on wings is analyzed on the basis of stereo particle image velocimetry measurements. All experiments regard a Reynolds number 0.87 × 106 flow around a rectangular wing with endplates and an aspect ratio of 2.0. The inherently unstable stall cell is stabilized by means of a localized spanwise disturbance. Velocity, vorticity, and Reynolds stress data above the wing and in the wake are presented and discussed, also in combination with Computational Fluid Dynamics data. The present study completes and clarifies the previously suggested models regarding the SC structure. The SC emerges in between the separation and trailing edge shear layer where three different types of vortices are identified: (a) the stall cell vortices that start normal to the wing surface and continue downstream aligned with the free stream, (b) the separation line vortex, and (c) the trailing edge line vortex that both run parallel to the wing trailing edge and grow significantly at the center of the stall cell. Analysis of the Reynolds stress data reveals high anisotropy. Concentration of high streamwise shear stress values is connected to the two shear layers and high cross shear Reynolds stresses are connected to vortex stretching. High normal Reynolds stress values are observed (a) in the separation but not in the trailing edge shear layer indicating the flapping of the former and (b) along the stall cell vortices indicating their wandering motion. The eddy viscosity based Reynolds averaged Navier-Stokes simulations are found in good qualitative agreement with the experiments in terms of the type and position of the identified vortex structures, an agreement which is linked to the correct trend in the predicted shear Reynolds stresses distributions. Quantitative deviations of the numerical results from the measurements are attributed to the isotropic definition of the turbulence model. Therefore, use of large eddy simulation is suggested for better prediction of the flow.

/pdf/study-of-a-stall-cell-using-stereo-particle-image-fq4tqhmbg1.pdf

Study of a stall cell using stereo particle image velocimetry

Experimental results and complimentary computations for airfoils with vortex generators are compared in this paper, as part of an e_ort within the AVATAR project to develop tools for wind turbine blade control devices. Measurements from two airfoils equipped with passive vortex generators, a 30% thick DU97W300 and an 18% thick NTUA T18 have been used for benchmarking several simulation tools. These tools span low-to-high complexity, ranging from engineering-level integral boundary layer tools to fully-resolved computational uid dynamics codes. Results indicate that with appropriate calibration, engineering-type tools can capture the e_ects of vortex generators and outperform more complex tools. Fully resolved CFD comes at a much higher computational cost and does not necessarily capture the increased lift due to the VGs. However, in lieu of the limited experimental data available for calibration, high _delity tools are still required for assessing the e_ect of vortex generators on airfoil performance.

Marinos Manolesos

Papers

Experimental investigation of the flow past passive vortex generators on an airfoil experiencing three-dimensional separation

Experimental and computational analysis of stall cells on rectangular wings

An Experimental Study of the Pultrusion of Carbon Fiber-Polyamide 12 Yarn

Study of a stall cell using stereo particle image velocimetry

Experimental benchmark and code validation for airfoils equipped with passive vortex generators