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

a cura di

Heat transfer to impinging isothermal gas and flame jets

The purpose of this review is to discuss the development and the state of the art in dynamic testing techniques and dynamic mechanical behaviour of rock materials. The review begins by briefly introducing the history of rock dynamics and explaining the significance of studying these issues. Loading techniques commonly used for both intermediate and high strain rate tests and measurement techniques for dynamic stress and deformation are critically assessed in Sects. 2 and 3. In Sect. 4, methods of dynamic testing and estimation to obtain stress–strain curves at high strain rate are summarized, followed by an in-depth description of various dynamic mechanical properties (e.g. uniaxial and triaxial compressive strength, tensile strength, shear strength and fracture toughness) and corresponding fracture behaviour. Some influencing rock structural features (i.e. microstructure, size and shape) and testing conditions (i.e. confining pressure, temperature and water saturation) are considered, ending with some popular semi-empirical rate-dependent equations for the enhancement of dynamic mechanical properties. Section 5 discusses physical mechanisms of strain rate effects. Section 6 describes phenomenological and mechanically based rate-dependent constitutive models established from the knowledge of the stress–strain behaviour and physical mechanisms. Section 7 presents dynamic fracture criteria for quasi-brittle materials. Finally, a brief summary and some aspects of prospective research are presented.

/pdf/a-review-of-dynamic-experimental-techniques-and-mechanical-2kstp2wfg4.pdf

A Review of Dynamic Experimental Techniques and Mechanical Behaviour of Rock Materials

Infrared thermography for condition monitoring – A review

Infrared thermography transforms the thermal energy, emitted by objects in the infrared band of the electromagnetic spectrum, into a visible image. This feature represents a great potentiality to be exploited in many fields, but this technique is still not adequately enclosed in industrial instrumentation because of a lack of adequate knowledge; at first sight, it seems too expensive and difficult to use. The aim of the present paper is to shortly overview existing work and to describe the most relevant experiences devoted to the use of infrared thermography in three main fields, i.e. thermo-fluid dynamics, technology and cultural heritage, which have been performed in the department the authors belong to. Results may be regarded from two points of view, either as validating infrared thermography as a full measurement instrument, or as presenting infrared thermography as a novel technique able to deal with several requirements, which are difficult to perform with other techniques. This study is also an attempt to give indications for a synergic use of the different thermographic methods and sharing experiences in the different fields.

http://iopscience.iop.org/article/10.1088/0957-0233/15/9/R01/pdf

Recent advances in the use of infrared thermography

This paper deals with the evolution of infrared (IR) thermography into a powerful optical tool that can be used in complex fluid flows to either evaluate wall convective heat fluxes or investigate the surface flow field behavior. Measurement of convective heat fluxes must be performed by means of a thermal sensor, where temperatures have to be measured with proper transducers. By correctly choosing the thermal sensor, IR thermography can be successfully exploited to resolve convective heat flux distributions with both steady and transient techniques. When comparing it to standard transducers, the IR camera appears very valuable because it is non-intrusive, it has a high sensitivity (down to 20 mK), it has a low response time (down to 20 μs), it is fully two dimensional (from 80 k up to 1 M pixels, at 50 Hz) and, therefore, it allows for better evaluation of errors due to tangential conduction within the sensor. This paper analyses the capability of IR thermography to perform convective heat transfer measurements and surface visualizations in complex fluid flows. In particular, it includes the following: the necessary radiation theory background, a review of the main IR camera features, a description of the pertinent heat flux sensors, an analysis of the IR image processing methods and a report on some applications to complex fluid flows, ranging from natural convection to hypersonic regime.

/pdf/infrared-thermography-for-convective-heat-transfer-56a0bwe7om.pdf

Infrared thermography for convective heat transfer measurements

Thermo-fluid-dynamics of submerged jets impinging at short nozzle-to-plate distance: A review

Non-destructive evaluation of aerospace materials with lock-in thermography

The aim of the present paper was to investigate the behaviour of glass fibres reinforced polymer (GFRP) under low velocity impact with infrared thermography. Several specimens were considered which include unidirectional E-glass fibres embedded in epoxy resin matrix with symmetrical stacking sequence [02/902]S. These specimens were impacted with modified Charpy pendulum by varying shape (ogival and hemispherical) and diameter (18 and 24 mm) of the hammer and the impact energy in the range 4–25 J. The side opposite to impact was monitored by infrared cameras. Sequences of images were acquired with starting and ending times set so as to include the evolution of thermal phenomena from thermo-elastic to thermoplastic phases. Infrared thermography was also used for non-destructive evaluation of specimens before and after impact. The obtained results show that on-line monitoring of the impact is useful for material characterization. In particular, it is shown that the onset of heat generation loci corresponds to the onset of impact damage. From the analysis of temperature maps it is possible to get information about damage threshold and extension. One main finding regards the relationship between the damaged area and the effective striking surface.

Giovanni Maria Carlomagno

Papers

Recent advances in the use of infrared thermography

Infrared thermography for convective heat transfer measurements

Thermo-fluid-dynamics of submerged jets impinging at short nozzle-to-plate distance: A review

Non-destructive evaluation of aerospace materials with lock-in thermography

Impact damage in GFRP: New insights with infrared thermography