Numerical Examination of Jets Induced by Multi-Bubble Interactions

Jets produced by the interaction of collapsing cavitating bubbles containing high-pressure gases can be utilized for wide variety of applications e.g. particle erosion, medical purposes (lithotripsy, sonoporation), tannery effluent treatment, etc. Among the many parameters, this jetting is largely influenced by spatial orientation of bubbles, their times of inception, relative bubble size ratio. In this context, multiple cavitating bubbles are able to generate numerous simultaneous jets, under suitable conditions, hence operating over a wider coverage area. Such multi-bubble arrangements can go a long way in enhancing the erosive impact on a target location even at cryogenic temperature (< 123 K) and hence necessitate investigation. In this paper, different configurations of multiple-bubble interactions are numerically simulated to examine jets directed towards a target location (fictitious particle, cell etc.) using computational fluid dynamics. No phase change is considered and the effect of gravity is neglected. The transient behaviour of the interface between the two interacting fluids (bubble and ambient liquid) is modelled using VOF (volume of fluid) method. In this paper, results obtained for different bubble configurations through numerical simulation are validated against suitable literature and further explored to assess the resulting jet effects. The time histories of interacting bubbles are presented and the consequent flow-fields are evaluated by the pressure and velocity distributions obtained. The same calculation is repeated in cryogenic environment and the results are compared. An attempt is made to approach towards an optimum arrangement and conditions for particle erosion.

Experimental Analysis of Air Flow in a Channel for Unconventional Radiator

The automotive industry is one of the fastest growing industries worldwide with millions of vehicle productions and sales every year globally. Some of the vehicles have their engines in rear end, which means there is no incoming airflow from the front and the engine cannot cool down efficiently. The main aim of the research is to study the flow behavior for a duct that can detour the incoming air to the radiator for vehicles those have their engines located at the back. The duct collects the incoming air from the front of the vehicle and detour it to the engine located at the back. This helps in cooling down the engine in order to protect it from being overheated. The research is conducted to understand the detailed parameters to be accounted for while designing such a prototype. It is important to understand the essence of a cooling effect as the efficiency of the vehicle engine can only be maintained under a stable temperature. The research is important as it can be applied to diverse engineering problems. There are three cases for the experiment, each with different lengths. However, the inlet and outlet have identical dimensions for all three cases. There is a certain scale factor used to scale down the dimensions from a previously studied CAD model. These scaled down dimensions are then utilized to fabricate the prototype. Once the model has been constructed, a mesh is located at the outlet, which helps recording velocity magnitude and direction at each of the respective node of the mesh. One of the key elements of the research is to extensively understand the type of flow at different points of the duct and how they affect the efficiency of the design. For example, the curved parts where channels are installed along the length of the duct experience turbulent air flow. Hence, it is important to understand the influence of these flows on the efficiency of the design.

Computational Investigation of Flow Over Geometry Compliant Lattice Structures

With the increasing prevalence of additive manufacturing, geometries that would not have been possible to manufacture just a few years ago are becoming a reality. One example is the ability to create pipes with integral, geometry compliant lattice structures. These compliant lattice structures offer the potential to greatly enhance heat transfer in arbitrary flow passages. This preliminary paper will focus on the development of an isothermal simulation model in OpenFOAM, to model the nature of the flow for a single unit cell, a unit cell screen, and a series of unit cell screens. Honeywell FM&T is a contractor of the U.S. Government under Contract No. DE-NA0002839.

Settling Characteristics of Polymeric Additives in Dodecane

Recent studies have shown that adding polymeric additives to hydrocarbon-based fuels can lead to suppression of their splashing behavior, as well as enhance their burning rates. However, there is a lack of objective data on polymeric additives settling times in these fuels. Choosing Dodecane as a representative of diesel-based fuels, present research experimentally investigates the settling behavior of polymeric additives (graphene) when mixed in with Dodecane, and the effects of various surfactants on such behavior. Methodology for experimental setup, data collection and data analysis is presented. Various concentrations of additives and surfactants are analyzed, and trends for settling times are shown.

Experimental Study of Chamber Volume Effect on Bubble Formation From Orifice Plates Submerged in Water

Experimental study of air bubble formation from orifice plates submerged in water pools has been carried out. Air is forced through the orifice by supplying it to a chamber connected to the orifice plate. The chamber volume plays an important role in determining the bubble growth time as well as bubble size and shape at departure. The effect of chamber volume is generally correlated in term of a dimensionless parameter, capacitance number (Nc), which is proportional to the chamber volume and is inversely proportional to the square of the orifice diameter. To better understand and characterize this effect, an experimental study is performed using ten orifice plates of diameter ranging from 0.61 mm to 2.261 mm with six different chamber volumes between 12 cc and 59 cc with the corresponding capacitance numbers varying from 0.2 to 19. The shape and size of the bubble are captured using high speed videography. The orifice plate material is acrylic glass which has an equilibrium contact angle of 38° with pure water. It was observed that the value of critical capacitance number or Nc above which the bubble evolution is affected by the gas chamber volume, is around 0.85. The bubbles are more spherical in shape, and the growth time is significantly smaller. Also, at high capacitance number (Nc > 7), the air flow in the bubble is so high that the bubble departs with a sharp apex and has a large volume. Above Nc > 10, the chamber effects plateau and further increase in gas chamber volume does not alter bubble size and shape at departure.

Analysis of Two-Phase Flow Slug Regime With Engineering Approach

In this research, the two-phase slug regime is investigated analytically with an engineering approach. due to the velocity gradient in the layers of the two-phase flow, numbers of waves form and grow in the liquid phase and may block the duct which in this case is called slug. Blocking the flow, it causes higher pressure accumulation which is the main reason of slug’s momentum through the duct. Simplifying the slug’s geometry and using basic physics laws yielded an equation between the slug’s back pressure and its length.

3D Modeling of the Thermal Phenomena During Laser Melting of Polymers

A comprehensive model of the selective laser sintering (SLS) process at the scale of the part is presented for application to polymeric powders. The powder bed is considered as a continuous medium with homogenized properties. A thermal model with detailed multiphysics coupling is presented. The model accounts for all elements of the thermal history : laser absorption, melting, coalescence, densification and volume shrinkage. For numerical resolution, a 3D in-house fortran code using FV method is developed. The proposed model is validated through the comparison of modeling data with experimental results available in the published literature. A parametric analysis about the thermal efficiency of the heating process against the laser energy input is proposed and the influence on the densification and thermal kinetics is discussed with regarding the evolution of the structure of the material.

Extracting Substantial Free Energy From Static Ambient Potential Energy Using Distance, Time-Lapse Chaos, and Coriolis Principles

Extracting free energy has long been a goal of science but is mostly considered impossible to achieve. Natural processes having independent movement, such as rivers and wind, are often used but provide varied effectiveness. However, coordinated instability within a statically pressurized ambience can be used to extract a significant percentage of the ambient potential energy. This method creates two pathways between two adjacent points, one being a chaotic or Coriolis swirling path and the other being a direct path, thereby creating a pressure difference between the two adjacent points, which can be harvested to reduce the kinetic energy input required to perform the process. While some refer to the proposed benefits as “perpetual motion,” it is necessary to understand that 55 to 80% of the required kinetic energy would still be mechanically generated; therefore, they could be better referred to as “coordinated chaos” or a “Coriolis energy extractor” to save energy [1]. This paper studies direct returns—extracting energy directly from a static (not dynamic) ambient energy. While such returns might not be substantial in normal activities, in deepwater or underground applications (e.g., oil or gas wells), they can be significant, often equating to a 20–45% reduction in fuel use or pollutant generation. In operations that use 20,000 horsepower, this could represent a savings of 4,000 horsepower or 10,000,000 Btu/hr with no associated financial costs.

Full Scale Testing of Pulse Jet Mixer Operating Control

A standard high-solids vessel (SHSV) concept design approach using pulse jet mixers (PJM) has been proposed by the US Department of Energy (DOE) for the Hanford Tank Waste Treatment and Immobilization Plant (WTP) as a potential replacement for several vessels that will be used to process highly radioactive waste. To assist with the evaluation of the SHSV concept, at DOE’s direction, the WTP Project recently completed qualification testing of the SHSV PJM mixing system to verify the design. Testing of the SHSV design, conducted at full scale, was split into two phases. The first phase of testing developed PJM controls that supported all operational modes under a set of most adverse fluid conditions. The second phase of testing used the PJM operating strategy, established during the first phase, to perform qualification testing to verify that the mixing system design supports the transfer, de-inventory, throughput, and sampling functional requirements of the SHSV. The different control methods that were used to operate PJMs in simulants exhibiting Newtonian and non-Newtonian rheological properties with high solids loading are presented. The PJM system of the SHSV uses six pulse tubes distributed in a circular array. Each pulse tube (3000 liters nominal volume) is connected to a jet pump pair (JPP) by means of an air link line. The JPP powers the PJM operation by applying a vacuum to refill the PJM (suction phase), pressurizing the PJM to discharge the pulse tube content at a target velocity (drive phase), and releasing the compressed air to allow the PJM to depressurize into a ventilation system (vent phase) designed for contaminated air. A PJM control system was developed to maximize the PJM operation and minimize potential impact to the structural integrity of the vessel. The experimental results showed effective control of the system parameters. The system response demonstrated reliable control of the drive set pressure, the drive time, and synchronization. The PJM control system design also proved robust in mobilizing settled solids.

The Impact of the Gas Temperature and of the Relative Humidity on the Performance of Fans Operating in Drying Plants

In order to investigate the impact of the gas temperature and its relative humidity on the performance of fans, the similarity laws for fans were extended and verified and numerical computations with the commercial CFD solver ANSYS CFX were performed. First the accuracy of the original fan laws was verified for different operating conditions. In a second step the influence of the temperature on the fan characteristics was investigated. Finally, to include the effect of the relative humidity multiphase simulations with air and water vapor were performed. Therefore, the relative humidity was analyzed for different gas temperatures. In such a way the full influence of the temperature and of the relative humidity on the performance characteristics of radial fans operating in drying plants was obtained. These numerical results have been analyzed in detail and compared with the results predicted by the presented extended similarity laws for turbomachines.