José Luis Santolaya

A framework about flow measurements by LDA–PDA as a spatio-temporal average: application to data post-processing

Phase Doppler anemometry (PDA) is a well-established technique to study two-phase flows and its principles are also used in laser Doppler anemometry (LDA) for measurements of fluid velocity. Raw measurements of individual particle data require post-processing to obtain useful and consistent information (moments of velocity, particle concentration and flux, velocity autocorrelation, etc). This is called in this paper the reconstruction of statistical information. In the 1970s, several basic algorithms to perform the statistical reconstruction were developed for LDA measurements (such as the transit time method, the inverse velocity method, etc). With the advent of PDA, the scientific community developed reconstruction algorithms to obtain mean variables of the dispersed phase. All these basic algorithms were expounded as unconnected methods, following independent threads not integrated into a general framework. Assuming that the PDA works under ideal conditions (all particles that cross the probe volume are validated), this paper provides a general formulation and fully systematizes a large set of previous statistical reconstruction methods. In this paper, the statistical reconstruction of both the dispersed and the continuous phase is unified: the continuous phase post-processing emerges as the same reconstruction method of the dispersed phase. The general framework proposed offers many advantages. First, some previous calculation methods of particle concentration turn out to be particular cases of this general formulation. Second, it provides an easy way to deduce unbiased estimators of any statistical parameter of the flow. Third, a wide set of new post-processing methods are proposed to be tested by any member of the scientific community. In the fourth place, the generalized integral method to compute the particle concentration also gives information about the probe volume geometry and two new auto-calibration algorithms are proposed: the integral calibration method and the cross-section integral calibration method. Finally, a physical interpretation of the statistical reconstruction process is provided: it is a spatio-temporal averaging of the detected particle data, and some of the algorithms used are related to the Eulerian–Eulerian mathematical description of multiphase flows.

Applying sustainability in product development

Sustainable product development initiatives have been evolving for some time to support companies improve the efficiency of current production and the design of new products and services through supply chain management. This work aims at integrating environmental criteria in product development projects at the same time that traditional product criteria are fulfilled. The manufacturing process of an airbrush was studied. Different strategies focused on the optimization of raw materials and energy consumption along the manufacturing operations, the identification of the product components that could be modified according to a DFA analysis, the evaluation of the recyclability rate for the materials making up the product and the identification of those materials with the highest environmental impact, were applied. An approach based on two main strategies, optimization of materials and optimization of processes is proposed to be used by engineering designers for a progressive education to eco-design practice.

Influence of liquid properties on ultrasonic atomization

Ultrasonic atomization is very convenient because it can generate droplets with diameters of a few microns andwith very narrow size distribution. Besides, opposite to twin fluid nozzles, in ultrasonic atomization, dropletgeneration and transport are decoupled processes. Droplets are ejected from the liquid surface with very lowvelocities, so driving them is relatively simple. Although this atomization method is now common in some specificapplications, for example in household humidifiers, there are still some details about the physics of this processthat are not completely understood. Up to date, most of the published results have been limited to experimentswith water. However, it has been demonstrated that atomization rates quickly decrease as liquid viscosityincreases. This work analyzes the characteristics of ultrasonic atomization of some alternative fluids to determineif there is any influence of other physical properties such as surface tension or vapor pressure. Experiments areperformed using a commercial piezoceramic disk with a resonance frequency of 1.65 MHz. The disk is excitedwith a sinusoidal signal with voltage amplitudes that go up to 60 V. Sprays are visually characterized analyzinginstantaneous images and high speed video sequences. Besides atomization rates are calculated by measuringthe weight loss in a fixed time. DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4588