Prediction of tip vortex cavitation inception on marine propellers at an early design stage

The inception of vortex cavitation at an early design stage is still difficult to forecast. The most reliable prediction of the full scale performance is achieved by means of model tests, which are possible for few designs only. A simplified model to calculate the inception of tip vortex cavitation is developed and tested. The model is based on results obtained from potential flow theory, using a boundary element method. The developed tip vortex cavitation inception model and also the panel method are described, after a short introduction to vortex cavitation. The numerical behaviour of the model is investigated for an elliptic wing at different angles of attack and two marine propellers in homogenous and not axially symmetric inflow. The cavitation model s properties concerning different Reynolds numbers are studied and the scale effects on calculated model- and full-scale tip vortices are discussed.http://deepblue.lib.umich.edu/bitstream/2027.42/84317/1/CAV2009-final143.pd

Vorticity Confinement methods for cavitating flows

Present work deals with investigations of numerical aspects of cavitating vortex dominated flows. Computations of the viscous flow on realistic, technical configurations require efficient methods and high grid resolution, which is not sufficient in most cases to capture important details of the flow. Insufficient resolution increases the numerical dissipation of vortices generated at the tip region of lifting surfaces. One possible solution to reduce the unphysical decay of the strength of the vortices (despite of moderate resolution) is the application of vorticity confinement methods. Aim of the paper is the development and the comparison of Vorticity Confinement (VC) methods for cavitating flows on unstructured grids. Applications are proposed to control devices and marine propulsion systems. The numerical dissipation of vortices is compared for different VC formulations. Especially the influence of the source terms on cavitating flows is investigated. The numerical computations are carried out by the finite volume solution method FreSCo on arbitrary grids. In the study vorticity confinement techniques are combined with different cavitation models available in the applied numerical method to investigate tip vortex flow. The cavitation models are based on Volume-of-Fluid (VoF). A NACA16020 elliptical wing is selected as a validation case. The combination of vorticity confinement formulations and cavitation models enables a better and a more detailed study of cavitation effects.http://deepblue.lib.umich.edu/bitstream/2027.42/84314/1/CAV2009-final139.pd

APPRAISEMENT OF THE GEOLOGIC FEATURES AS A GEO-HERITAGE IN ABU-ROASH AREA, CAIRO- EGYPT

Egypt contains Geologic Heritage that create much opportunity to develop educational and recreational programs as well as tourism projects. Enhancement of Geologic Heritage and awareness of the importance of Geologic Heritage is a great challenge. This paper focuses on a neglected area inside Cairo that is facing a great destruction from the people living there. The Abu-Roash archaeological site is located at 31ᵒ 02′ 42″ E longitude and 30ᵒ 02′ 42″ N latitude. It is one of the most important areas for education and scientific study inside Cairo. Although the area is not suited as a geo-heritage or even a protected area, it contains Cretaceous to upper Eocene sedimentary beds and fossils, and a great variety of structural features. Not only an important geologic aspect found in the area but also an archeological site is present which provide the area of a great scientific, cultural/historical, aesthetic and/or social/economic value. These different criteria qualifies the study are to have a regional/provincial rank for its Geo-heritage. Abu Roash area are possess good geo-diversity, geo abundance and geo richness which lead us to start point for establishing potential geo-heritage that should be conserved the area also need to be recognized as a geological conservation sites, the area should be Stated as a protected area of a heritage legislation to protect geo-heritage

Coffee grounds as a soil conditioner: Effects on physical and mechanical properties – II. Effects on mechanical properties

Applying coffee grounds (CG) to sandy, calcareous, and clayey soils resulted in notable effects on soil expansion, cracking, cohesion, internal friction, initial stress and resistance to penetration. In sand, expansion upon saturation was greater after wetting-and-drying cycles. Highest increases were 15.71%, 16.14% and 31.86% for sandy, calcareous and clayey soils, respectively. Effect of CG on cracking was negligible in sand and very slight (<1.0%) in the calcareous soil but marked in clay (14.18% at 10% CG). In sand, cohesion (c) increased significantly with CG up to the 10% content. Cohesion increased by 2.5-folds and 4.5-folds at 5% and 10% CG, respectively. The presence of fine CG grains among larger sand particles, boosted microbial activities, and the resulting cementing and binding effects resulted in increased cohesion. For calcareous soil, cohesion rose from 0.04 kg∙cm-2 to 0.13 kg∙cm-2 as CG increased from 0% to 15%. In clay, maximum cohesion (0.20 kg∙cm-2) was associated with the 10% CG and was highest of all soils. In sand, the angle of internal friction (φ) decreased notably as CG increased from 5% to 10% but there was no consistent pattern in any of the soils. An increase in initial stress (pi) was observed between 0% and 10% CG in sand and between 0% and 15% in calcareous soil while clay showed no particular trend. Patterns of pi were, thus, consistent with those of cohesion for all soils. Resistance to penetration increased substantially with CG in sand. The effect in calcareous and clayey soils took an opposite trend to that of sand and resistance was generally higher in calcareous soil. Overall effects of CG on resistance were desirable in all soils as far as agriculture (seedling emergence, crop growth, irrigation, etc.) is concerned

Coffee Grounds as a Soil Conditioner: Effects on Physical and Mechanical Properties - I. Effects on Physical Properties

Coffee grounds (CG) improved some soil physical properties (dry density, gd; porosity, n; aggregation; hydraulic conductivity, Ks; and infiltration rate, IR). Effects on other properties were inconsistent (e.g., sorptivity, S), or unfavorable (e.g., available water, AW). gd decreased and n increased with CG. CG decreased Ks in sand. In calcareous soil, maximum increase was associated with 10% and 15% CG before and after wetting-and-drying cycles (WDC), respectively. Ks increased with CG in clay, with greatest increase attained at 10% CG. IR decreased with CG in sand. In calcareous and clayey soils, IR decreased with CG before WDC but increased after WDC where maximum increase in clay was linked to 10% CG. No solid trends of soil sorptivity, S, were identified. Before WDC, S had the order: sand > calcareous > clay. For most cases, adding CG increased total water holding capacity (WHC). However, after WDC, the increase in water content at field capacity (FC) with CG was accompanied by a greater increase in wilting point (WP) and therefore a decrease in AW. CG improved soil structure and aggregation and increased non-water-stable aggregates in calcareous and clayey soils. Mean weight diameter (MWD) indicated increase in water-stable aggregates in sand at 5% and 10% CG. In clay, MWD increased only at 5% CG. Although results did not show coherent responses with some tested properties, they, mostly, indicate some beneficial effects of CG, particularly in relation to improving aggregation and water flow

Salp Swarm Optimization with Self-Adaptive Mechanism for Optimal Droop Control Design

The collaboration of the various distributed generation (DG) units is required to meet the increasing electricity demand. To run parallel-connected inverters for microgrid load sharing, several control strategies have been developed. Among these methods, the droop control method was widely accepted in the research community due to the lack of important communication links between parallel-connected inverters to control the DG units within a microgrid. To help to solve the power-sharing process, keep to frequency and voltage constrained limits in islanded mode microgrid system. The parameter values must therefore be chosen accurately by using the optimization technique. Optimization techniques are a hot topic of researchers; hence This paper discusses the microgrid droop controller during islanding using the salp swarm inspired algorithm (SSIA). To obtain a better fine microgrid output reaction during islanding, SSIA-based droop control is used to optimally determine the PI gain and the coefficients of the prolapse control. The results of the simulation show that the SSIA-based droop control can control the power quality of the microgrid by ensuring that the keep to frequency and voltage constrained limits and deviation and proper power-sharing occurs during the microgrid island mode during a load change

Citrus aurantium l. Active constituents, biological effects and extraction methods. an updated review

Citrus genus is a prominent staple crop globally. Long-term breeding and much hybridization engendered a myriad of species, each characterized by a specific metabolism generating different secondary metabolites. Citrus aurantium L., commonly recognized as sour or bitter orange, can exceptionally be distinguished from other Citrus species by unique characteristics. It is a fruit with distinctive flavor, rich in nutrients and phytochemicals which possess different health benefits. This paper presents an overview of the most recent studies done on the matter. It intends to provide an in-depth understanding of the biological activities and medicinal uses of active constituents existing in C. aurantium. Every plant part is first discussed separately with regards to its content in active constituents. All extraction methods, their concepts and yields, used to recover these valuable molecules from their original plant matrix are thoroughly reported

Impact of Knowledge and Attitude on Saudis’ Physical Activity Practice and Inactivity Barriers: A Questionnaire-based Study

BACKGROUND: Community participation in physical activity is considered a major public health preference of WHO. Saudi Arabia in the last decades faced many tremendous economic changes leading to adoption of western dietary habits associated with sedentary lifestyle. AIM: We aimed to study the relationship between both physical activity knowledge and attitude of community to the practice of individuals. METHODS: We used a questionnaire consists of a mixture of closed-ended questions. Participants were recruited through direct meetings in local markets, schools, and workplaces. Seven hundred and sixty six individuals agreed to participate. RESULTS: Overall correct answers to questions about importance of physical activity were 76.58%. The predominance of participants’ attitude was to establish public places for physical activity in each neighborhood (92.1%). Participants acknowledged that they exercise to improve their health (47.5%). Participants mainly perform light exercises (47.2%) on basis of 1–3 times weekly (48.9%). About 90.8% of participants admitted that they like to increase duration of their physical activity. CONCLUSIONS: Overall physical activity practice of participants’ needs encourage overcoming obstacles that prevent individuals from practicing especially lack of time