Insect-proof screens constitute a physical means of protecting crops and their use has become widespread in recent years. There is no doubt as to their efficiency in controlling insects, but they do have a negative influence on greenhouse ventilation as they obstruct air-flow. It is therefore necessary not only to evaluate their efficiency as a means of protecting crops, but also to estimate the degree to which they obstruct airflow. To this end the present work analyses the aerodynamic characteristics of these screens, carrying out experiments with two devices which force a flow of air through them, thus providing data of the pressure drop as a function of air velocity. The analysis of these data has provided simple ratios of the permeability and the inertial factor as a single function of porosity.

ISHS International Conference on Sustainable Greenhouse Systems - Greensys2004 CONTRIBUTION TO CHARACTERISATION OF INSECT-PROOF SCREENS: EXPERIMENTAL MEASUREMENTS IN WIND TUNNEL AND CFD SIMULATION

The electrical penetration graph (EPG) technique is the most powerful tool for studying the feeding behavior of pierce-sucking insects. However, calculating EPG variables is often very time-consuming, and consequently, several software programs have been developed for the automatic calculation of EPG variables. Here we present a new user-friendly Excel Workbook that uses a standardized list of EPG variables and follows expert guidelines for calculating them. The program developed in Visual Basic for Applications (VBA) is a step up from the existing software and allows easy data analysis and interpretation. It also includes a novel option for dealing with the common problem of “truncated”—waveforms artificially terminated by the end of recording. The only requirement to run the program is Microsoft Excel software running under a PC environment. The Workbook was validated by calculating variables from EPG recordings of aphids and psyllids and the results obtained were compared with those of existing software such as the Sarria Workbook. Our EPG Workbook provides researchers with a reliable and standardized tool for the automatic calculation of up to 127 EPG variables from phloem-sap-sucking insects.

Currently, the porous surface of the screens is measured on digital images taken by microscope representing the orthogonal projection of the textiles. It is known that this way of measuring the porous surface underestimate largely the real hole surface. To improve this aspect, in this work the hole surface is identified as a specific region of the hyperbolic paraboloid and a methodology is developed to address its calculation. Indeed, the results show that the porous surface measured on orthogonal projection is significantly less than the real hole surface. However, the application of this methodology is very complex and for this reason an approximate alternative method that considerably simplifies the difficulty of the problem is proposed. The results obtained by one and another method have small discrepancies so that the approximate method is also a good option for the calculation of the porous surface of these textiles.