The boundary layer equations for plane, incompressible, and steady flow are 

$$\matrix{ {u{{\partial u} \over {\partial x}} + v{{\partial u} \over {\partial y}} = - {1 \over \varrho }{{\partial p} \over {\partial x}} + v{{{\partial ^2}u} \over {\partial {y^2}}},} \cr {0 = {{\partial p} \over {\partial y}},} \cr {{{\partial u} \over {\partial x}} + {{\partial v} \over {\partial y}} = 0.} \cr }$$

Boundary Layer Theory

To improve the performance of particle image velocimetry in measuring instantaneous velocity fields, direct cross-correlation of image fields can be used in place of auto-correlation methods of interrogation of double- or multiple-exposure recordings. With improved speed of photographic recording and increased resolution of video array detectors, cross-correlation methods of interrogation of successive single-exposure frames can be used to measure the separation of pairs of particle images between successive frames. By knowing the extent of image shifting used in a multiple-exposure and by a priori knowledge of the mean flow-field, the cross-correlation of different sized interrogation spots with known separation can be optimized in terms of spatial resolution, detection rate, accuracy and reliability.

Theory of cross-correlation analysis of PIV images : Image analysis as measuring technique in flows

The Structure of Turbulent Shear Flow By Dr. A. A. Townsend. Pp. xii + 315. 8¾ in. × 5½ in. (Cambridge: At the University Press.) 40s.

/pdf/the-structure-of-turbulent-shear-flow-2yf3szhaqb.pdf

The Structure of Turbulent Shear Flow

Polyurethanes (PUs) are a class of versatile materials with great potential for use in different applications, especially based on their structure–property relationships. Their specific mechanical, physical, biological, and chemical properties are attracting significant research attention to tailoring PUs for use in different applications. Enhancement of the properties and performance of PU-based materials may be achieved through changes to the production process or the raw materials used in their fabrication or via the use of advanced characterization techniques. Clearly, modification of the raw materials and production process through proper methods can produce PUs that are suitable for varied specific applications. The present study aims to shed light on the chemistry, types, and synthesis of different kinds of PUs. Some of the important research studies relating to PUs, including their synthesis method, characterization techniques, and research findings, are comprehensively discussed. Herein, recent advances in new types of PUs and their synthesis for various applications are also presented. Furthermore, information is provided on the environmental friendliness of the PUs, with a specific emphasis on their recyclability and recoverability.

https://ir.unikl.edu.my/jspui/bitstream/123456789/15237/1/Polyurethane%20types%2c%20synthesis%20and%20applications%20%e2%80%93%20a%20review.pdf

Polyurethane types, synthesis and applications – a review

Evaluation and prediction of the tensile properties of continuous fiber-reinforced 3D printed structures

The influence of initial flow conditions on the passive scalar field of a turbulent free jet issuing from the round nozzle is investigated in this paper by a review of the literature and a detailed experimental study. Two sets of distinctly different initial conditions are generated using two nozzle types: a smooth contraction and a long straight pipe. The present measurements of the passive scalar (temperature) field were conducted in a slightly heated air jet from each nozzle at a Reynolds number of 16 000 using identical experimental facilities and a single measurement technique. Significant differences between the flows from the two nozzles are revealed throughout the measured flow region which covers the axial range from 0 to 70 jet exit diameters. The study suggests that the differences observed in the statistics of the scalar field may be related to differences in the underlying turbulence structure of the jet in the near field. The present findings support the analytical result of George (1989) that the entire flow is influenced by the initial conditions, resulting in a variety of self-similar states in the far field.

/pdf/influence-of-jet-exit-conditions-on-the-passive-scalar-field-1nfxcs914g.pdf

Influence of jet exit conditions on the passive scalar field of an axisymmetric free jet

The differences in mixing performance between axisymmetric turbulent jets issuing from three common types of nozzle, viz. a contoured (or smooth contraction) nozzle, a sharpedged orifice and a long pipe, are investigated. The investigation is carried out using both qualitative flow visualizations and quantitative measurements of the centerline passive temperature. It is revealed that the jet issuing from an orifice plate provides the greatest rate of mixing with ambient fluid, while the pipe jet has the lowest rate. Physical insight into the differences is explored using a planar imaging technique and measurements of power spectra of the fluctuating velocity

Mixing Characteristics of Axisymmetric Free Jets From a Contoured Nozzle, an Orifice Plate and a Pipe

Impacts of a jet's exit flow pattern on mixing and combustion performance

Material extrusion additive manufacturing (MEAM), also known as three-dimensional (3D) printing, is a popular additive manufacturing technique suitable for producing 3D shapes using thermoplastic materials. The majority of companies that design and test 3D printing machines work with thermoplastic acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) filaments. It is, however, crucial to utilize different types of filaments for a broader range of applications with different mechanical property requirements. Shape memory polymers (SMPs) are smart materials that react to an applied stimulus in order to recover large strains. MEAM techniques may be used for the production of SMP-based parts, allowing for smart structures to be created in a wide variety of geometries. In this work, a commercial 3D-printer was used to produce 3D printed polyurethane-based SMP specimens. An annealing heat treatment was applied to some of the specimens. Mechanical and thermomechanical testing was conducted to study the effects of testing temperatures and annealing heat treatments on the tensile and shape memory properties of the samples. 3D printing was shown to be a suitable technique for producing SMP parts capable of retaining good shape memory characteristics. Different annealing heat treatments and test temperatures were found to have considerable effects on the SMP specimen properties. In particular, annealing the specimens at 85 °C for 2 h helped to improve the rate of shape recovery and the consistency of mechanical test results.

Characterization of polyurethane shape memory polymer processed by material extrusion additive manufacturing

https://sites.ualberta.ca/~jos/pbl/inci_preprint.pdf

David S. Nobes

Papers

Influence of jet exit conditions on the passive scalar field of an axisymmetric free jet

Mixing Characteristics of Axisymmetric Free Jets From a Contoured Nozzle, an Orifice Plate and a Pipe

Impacts of a jet's exit flow pattern on mixing and combustion performance

Characterization of polyurethane shape memory polymer processed by material extrusion additive manufacturing

Effect of geometry on the mechanisms for off-bottom solids suspension in a stirred tank