Control of Runoff Peak Flow for Urban Flooding Mitigation

Urban flooding has become a serious but not well-resolved problem during the last decades. Traditional mainstream facilities, such as vegetated roofs, permeable pavements, and others, are effective to eliminate urban flooding only in case of small rains because the water-retaining and detaining capacities of these traditional facilities are limited. Here, we propose a new buffer tank buried in soil to deal with rainwater onsite as peak-flow control for urban flooding mitigation. Experiments showed that the buffer tank intercepts the surface runoff and discharges the intercepted water through a designed outlet orifice. By properly setting the cross-sectional area of the orifice, the tank extends the drainage duration several times longer than that of the rainfall duration. It is found that the buffer tank attenuates the peak flow greater at heavier rain. At small rain (<2.5 mm), the tank is always unfilled, preserving storage spaces for detaining rainwater in case of heavy rain. The buffer tank is thus greatly helpful to mitigate the flooding problem, avoiding being saturated by small long-lasting rain.

Alternative Geometric Arrangements of the Nozzle Outlet Orifice for Liquid Micro-Jet Focusing in Gas Dynamic Virtual Nozzles

Liquid micro-jets are crucial for sample delivery of protein crystals and other macromolecular samples in serial femtosecond crystallography. When combined with MHz repetition rate sources, such as the European X-ray free-electron laser (EuXFEL) facility, it is important that the diffraction patterns are collected before the samples are damaged. This requires extremely thin and very fast jets. In this paper we first explore numerically the influence of different nozzle orifice designs on jet parameters and finally compare our simulations with the experimental data obtained for one particular design. A gas dynamic virtual nozzle (GDVN) model, based on a mixture formulation of Newtonian, compressible, two-phase flow, is numerically solved with the finite volume method and volume of fluid approach to deal with the moving boundary between the gas and liquid phases. The goal is to maximize the jet velocity and its length while minimizing the jet thickness. The design studies incorporate differently shaped nozzle orifices, including an elongated orifice with a constant diameter and an orifice with a diverging angle. These are extensions of the nozzle geometry we investigated in our previous studies. Based on these simulations it is concluded that the extension of the constant diameter channel makes a negligible contribution to the jet’s length and its velocity. A change in the angle of the nozzle outlet orifice, however, has a significant effect on jet parameters. We find these kinds of simulation extremely useful for testing and optimizing novel nozzle designs.

The Use of Air Induction Nozzles for Application of Fertilizing Preparations Containing Beneficial Microorganisms

The work presents the structure and characteristics of field sprayer nozzles, as well as their impact on the survival of beneficial organisms in the selected fertilizing preparations. EŻK and EŻKT nozzles, (EŻK and EŻKT are trade names of single and twin jet air induction nozzles, respectively), that are available on the market have shown low efficiency in the discussed characteristics. Survival of microorganisms under initial conditions at 13.6 × 106 cfu/mL and pressure of 0 MPa, under critical conditions dropped to 1.7 × 106 cfu/mL for EŻK02 and 1.2 × 106 cfu/mL for EŻKT02, in both variants at a pressure of 0.5 MPa. When increasing the flow rate of the components, i.e., the size of the outlet orifices, it was observed that the survival of microorganisms increased by about 11.3% compared to the previously tested component. This resulted from the negative impact of the following: the pressure generated by the application device, number of outlet orifices, and size of an outlet orifice. The results of survival of microorganisms are given in the colony-forming unit (CFU). In addition to providing guidelines useful in the creation of a prototype sprayer intended for use in the application of microbiological preparations, the presented characteristics are a source of information for the end user as regards the proper conditions for the application of these preparations.

A Novel Buffer Tank to Attenuate the Peak Flow of Runoff

Impermeable pavements and roofs in urban areas convert most rainfall to runoff, which is commonly discharged to local sewers pipes and finally to the nearby streams and rivers. In case of heavy rain, the peak flow of runoff usually exceeds the carrying capacity of the local sewer pipes, leading to urban flooding. Traditional facilities, such as green roofs, permeable pavements, soakaways, rainwater tanks, rain barrels, and others reduce the runoff volume in case of a small rain but fail in case of a heavy rain. Here we propose a novel rainwater buffer tank to detain runoff from the nearby sealed surfaces in case of heavy rain and then to discharge rainwater from an orifice at the tank’s bottom. We found that considering a 100m2 rooftop with 0.80 runoff coefficient and a 10cm rainfall depth for an hour, a cubic tank with internal edge side of a square of 2 m attenuates the peak flow about 45%. To reduce a desirable peak flow, the outlet orifice of the buffer tank must be optimized according to site-specific conditions. The orifice can be set at an elevation from the tank’s bottom to create a dead storage for harvesting rainwater.

Numerical and experimental study of a jet impinging with axial symmetry with a set of heat exchanger tubes

The main purpose of this research is to predict the flow field of impinging turbulent jet with cylinder in a 3-d state. Nowadays, shear stress has multiple uses in the industry. The study has been conducted in both compressible and incompressible states with output velocities between 100 and 150 m/s, in different eccentricities of jet with respect to the first cylinder, and in various nozzle outlet orifice distances from front edge of the first cylinder. Pressure distribution and shear stress on cylinder surfaces have been determined and efficiency of jet in cleaning the heat exchangers pipes has been analyzed. Also, an experimental investigation has been conducted in order to verify the accuracy of the numerical results. Results show that if the distance between nozzle outlet orifice and the front edge of the first cylinder (L) equals 1.52 D (D is the diameter of the cylinder), the jet has the highest cleaning effect.

Prediction of cavitation and induced erosion inside a high-pressure fuel pump

The operation of a high-pressure, piston-plunger fuel pump oriented for use in the common rail circuit of modern diesel engines for providing fuel to the injectors is investigated in this study from a numerical perspective. Both the suction and pressurization phases of the pump stroke were simulated with the overall flow time being in the order of 12 × 10−3 s. The topology of the cavitating flow within the pump configuration was captured through the use of an equation of state implemented in the framework of a barotropic, homogeneous equilibrium model. Cavitation was found to set in within the pressure chamber as early as 0.2 × 10−3 s in the operating cycle, while the minimum liquid volume fraction detected was in the order of 60% during the second period of the valve opening. Increase in the in-cylinder pressure during the final stages of the pumping stroke leads to the collapse of the previously arisen cavitation structures and three layout locations, namely, the piston edge, the valve and valve-seat region and the outlet orifice, were identified as vulnerable to cavitation-induced erosion through the use of cavitation aggressiveness indicators.

A Portable Handheld Oxygen Blender: A Novel Design to Reduce Early Oxygen Toxicity

Oxygen is an essential therapeutic agent used extensively in all hospitals for patients with compromised function of the respiratory or cardiac systems. All patients (with the exception of neonates with certain heart diseases) are resuscitated with 100% oxygen. The American Heart Association Guidelines for Resuscitation state that it is essential in the post-resuscitative phase to decrease the concentration of O2 provided to keep oxyhemoglobin saturation (SpO2) > 94%, with a goal of avoiding hyperoxia while ensuring adequate oxygen delivery. Hyperoxia has been shown to be responsible for worsening tissue injury via oxidative damage following ischemia-reperfusion. Therefore, it is important in the post-resuscitative phase to use the lowest inspired oxygen concentration (FiO2) that will maintain SpO2 ≥ 94%. To address this, clinicians use oxygen blenders: devices that mix room air (21% O2) and medical grade oxygen (100% O2) to create a desirable FiO2. Current oxygen blenders have the disadvantage of being wall-mounted, bulky, and are limited to a small set of oxygen delivery devices (nebulizers, mechanical ventilators) with which they can interface. We developed an oxygen blending device capable of mixing room air and 100% O2 using the venturi principle. The device features a cylindrical body with a venturi nozzle and an entrainment window. It is handheld, portable, and machined from acrylic plastic. An oxygen blender with these features allows for appropriate oxygen therapy during patient transport. As oxygen flows through the device from the inlet orifice, atmospheric air is drawn in through the window, mixed, and then delivered to the patient through the outlet orifice. We designed the outlet orifice to have the same dimensions as the inlet orifice, allowing for universal integration with any device that connects to standard oxygen tubing. The entrainment window area can be adjusted by twisting a cover over the body of the blender, thus adjusting the FiO2 delivery. Using a venturi nozzle of 6.35 mm in diameter and an entrainment window area of 97 mm2, we achieved FiO2 ranging from 40% to 50% using input flow of 100% O2 at 6 L/min at 50 psi (via rotameter). The key feature of this device is that it can be interposed between any standard oxygen tubing allowing control of FiO2 at the bedside of the patient in hospital or during transport. Further work is needed to achieve a wider FiO2 range.

The Influence of Orifice Insertion for Low Noxious Emissions from Combustion System

This paper presents the effect of inserting swirler outlet orifice plate of different sizes at the exit plane of the radial air swirler in liquid fuel burner system. Tests were carried out with three different orifice plates with area ratios (orifice area to swirler exit area ratio) between 0.7 and 1.0 using 280 mm inside diameter combustor of 1000 mm length. Several tests were conducted using the commercial diesel as fuel. The fuel was injected at the back plate of the 45o vane angle swirler outlet using a central fuel injector with a single fuel nozzle pointing axially outwards. The aim of the insertion of orifice plates is to create the swirler pressure loss at the swirler outlet phase in order to maximise the swirler outlet shear layer turbulence to assist the fuel/air mixing. In the present work, the orifice plate with smaller area ratios exhibited very low NOX emissions for the whole operating equivalence ratios. The NOX reduction of more than 20 percent is achieved for orifice with 0.7 area ratio compared to 1.0 area ratio. Other emission such as carbon monoxide is increased with the decrease in the orifice area ratios. The results from this experiment show that good combustion is achieved by using smallest area ratios of orifice plate.