scholarly journals Numerical Modelling of the Ultrasonic Treatment of Aluminium Melts: An Overview of Recent Advances

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3262 ◽  
Author(s):  
Bruno Lebon ◽  
Iakovos Tzanakis ◽  
Koulis Pericleous ◽  
Dmitry Eskin
Keyword(s):  
Best Practice ◽  
Acoustic Pressure ◽  
Pressure Field ◽  
State Of The Art ◽  
Liquid Metals ◽  
Numerical Models ◽  
Acoustic Cavitation ◽  
Velocity Fields ◽  
Melt Processing ◽  
Best Practice Guidelines

The prediction of the acoustic pressure field and associated streaming is of paramount importance to ultrasonic melt processing. Hence, the last decade has witnessed the emergence of various numerical models for predicting acoustic pressures and velocity fields in liquid metals subject to ultrasonic excitation at large amplitudes. This paper summarizes recent research, arguably the state of the art, and suggests best practice guidelines in acoustic cavitation modelling as applied to aluminium melts. We also present the remaining challenges that are to be addressed to pave the way for a reliable and complete working numerical package that can assist in scaling up this promising technology.

Simulations of Experiments on Isothermal Containment Atmosphere Mixing Caused by Vertical Injection

2020 ◽  
Author(s):  
Rok Krpan ◽  
Iztok Tiselj ◽  
Ivo Kljenak
Keyword(s):  
Best Practice ◽  
Molecular Diffusion ◽  
Numerical Models ◽  
Three Dimensional ◽  
Momentum Equation ◽  
Correction Function ◽  
Best Practice Guidelines ◽  
Air Jet ◽  
Calculation Results ◽  
Definition Of

Abstract An experiment performed in SPARC experimental facility, was simulated with the computational fluid dynamics code OpenFOAM. The experiment took place in two phases. In the first phase, a helium-air layer was generated, which was then eroded with a vertical air jet injected in the vessel axis during the second experimental phase. A three-dimensional and a quasi-two-dimensional numerical models of a cylindrical vessel were developed and mesh convergence studies were performed. The mixing process was simulated as a single-phase flow with common momentum equation. Included gas species mass fractions are considered as passive scalars and are calculated using the transport equation. However, term describing the molecular diffusion cannot be neglected in our case and had to be added to diffusion equation implemented in default OpenFOAM solver. The k-ε turbulence model with additional buoyancy term implemented in OpenFOAM was used for turbulence modelling. Despite improvement of the physical model and following the Best Practice Guidelines, the results obtained with OpenFOAM CFD code still, at some locations, differ substantially from the experimental results. A modified definition of low Reynolds number eddy viscosity correction function is proposed, which significantly improves the agreement between measurements and calculation results.

scholarly journals What Is Unique about the New Canadian COPD Guidelines?

2004 ◽  
Vol 11 (3) ◽  
pp. 200-203 ◽  
Author(s):  
Denis E O'Donnell
Keyword(s):  
Chronic Obstructive Pulmonary Disease ◽  
Older Women ◽  
Family Physician ◽  
Best Practice ◽  
State Of The Art ◽  
Chronic Obstructive ◽  
Optimal Management ◽  
Obstructive Pulmonary Disease ◽  
Death Rates ◽  
Best Practice Guidelines

The prospect of digesting yet another set of ?best practice? guidelines is not an appealing one for the overwrought family physician. The Canadian Thoracic Society (CTS) panel, charged with the enormous task of developing new evidencebased recommendations, was acutely aware of this. Nevertheless, they were convinced that the time was right to tackle this important educational initiative, and somehow managed to summon considerable reserves of energy and enthusiasm to produce an excellent, state-of-the-art compendium on the optimal management of this condition (1). Faced with the evidence that death rates from chronic obstructive pulmonary disease (COPD) continue to escalate in Canada and that its prevalence has risen to unprecedented levels (particularly in older women), the panel believed that there was an urgent need to raise awareness of this disease, and to optimize diagnosis and management (2).

Ultrasound Actuation of Shape-Memory Polymer Filaments: Acoustic-Thermoelastic Modeling and Testing

2017 ◽  
Author(s):  
Aarushi Bhargava ◽  
Kaiyuan Peng ◽  
Jerry Stieg ◽  
Reza Mirzaeifar ◽  
Shima Shahab
Keyword(s):  
Drug Delivery ◽  
Shape Memory ◽  
Shape Recovery ◽  
Acoustic Pressure ◽  
Pressure Field ◽  
Numerical Models ◽  
Splitting Method ◽  
Water Tank ◽  
Source Power ◽  
Time Frequency

Controlled drug delivery (CDD) technology has received extensive attention in the past three decades due to numerous advantages of this technology when compared to the conventional methods. Despite recent efforts and substantial achievements, controlled drug releasing systems still face major challenges in practice, including chemical issues with synthesizing biocompatible drug containers and releasing the pharmaceutical compounds at the targeted location with a controlled time rate. In this work, we present experimentally-validated acoustic-thermoelastic mathematical modeling to show the feasibility of using shape memory polymers (SMPs) and focused ultrasound (FU) technology for designing a novel drug-delivery system. SMPs represent a new class of materials that have the ability of storing a temporary shape and returning to their permanent or original shape when subjected to external stimuli such as heat. FU is used as a trigger for noninvasively stimulating SMP-based drug capsules. FU has a superior capability to localize the heating effect, thus initiating the shape recovery process only in selected parts of the polymer. A multiphysics model is developed, which optimizes the design of a SMP-based CDD system using acoustic-thermoelastic analysis of a filament as the constituting base structure and quantifies its activation through FU. The analytical and numerical models are divided into three parts. The first part studies the acoustic behavior of SMPs using Khokhlov-Zabolotskaya-Kuznetsov (KZK) model. The equation solves for acoustic pressure field in a hybrid time-frequency domain using operator-splitting method and examines the effects of absorption, diffraction and nonlinear distortion on the propagating wave in the medium. The second part provides a numerical model based on Penne’s Bioheat equation to estimate the thermal field developed in SMPs as a result of focused acoustic pressure field. The third part provides a numerical framework to predict the mechanical stresses developed in SMPs under FU and consequent shape recovery. The mechanical model is formulated by a compressible neo-Hookean constitutive equation, which assumes the SMPs behave as a thermoelastic material and predicts the shape memory effect under FU. Experimental validation is performed using a FU transducer in a water tank. The recovery of thermally responsive SMPs under FU predicted by our model shows a good accordance with the experiments. The modeling results are used to optimize parameters such as nonlinear properties, input frequency, source power and dimensional effects to achieve maximum shape recovery.

On Influence of Turbulence Modelling on Cavitation Prediction for Flow Around P1356 Ship Propeller

2008 ◽  
Author(s):  
Conxita Lifante ◽  
Thomas Frank ◽  
Karsten Rieck
Keyword(s):  
Best Practice ◽  
Pressure Field ◽  
Numerical Solutions ◽  
Turbulence Modeling ◽  
Turbulence Models ◽  
Transient Pressure ◽  
Turbulent Structures ◽  
Pressure Oscillations ◽  
Best Practice Guidelines ◽  
Ship Propeller

The goal of this work is to get a deeper understanding of the structure of the flow around a propeller of a passenger ship, specially the pressure field, where turbulent fluctuations and cavitation can lead to pressure oscillations, vibration and noise. The accurate prediction of cavitation has been found out to be intrinsically related to the accurate resolution of turbulent structures of the flow. Therefore, a thoroughly analysis of the turbulence modeling in this kind of application was performed. Following the Best Practice Guidelines (BPG) [1] different grids and turbulence models have been investigated. The numerical results obtained have been compared to the experimental data generated at SVA Potsdam, which includes transient pressure signals as well as cavitation patterns. A highly satisfactory agreement between numerical solutions and experiments is observed for the finest grids and a scale-resolving turbulence modeling approach (DES/SAS).

Opioid crisis in primary care? An audit of high-dose opioid prescribing at Bangholm GP Practice

2020 ◽  
Vol 70 (suppl 1) ◽  
pp. bjgp20X711581
Author(s):  
Charlotte Greene ◽  
Alice Pearson
Keyword(s):  
Chronic Pain ◽  
Back Pain ◽  
Practice Guidelines ◽  
Best Practice ◽  
Evidence Base ◽  
High Dose ◽  
Opioid Prescription ◽  
Opioid Prescribing ◽  
Best Practice Guidelines

BackgroundOpioids are effective analgesics for acute and palliative pain, but there is no evidence base for long-term pain relief. They also carry considerable risks such as overdose and dependence. Despite this, they are increasingly prescribed for chronic pain. In the UK, opioid prescribing more than doubled between 1998 and 2018.AimAn audit at Bangholm GP Practice to understand the scale of high-strength opioid prescribing. The aim of the audit was to find out if indications, length of prescription, discussion, and documentation at initial consultation and review process were consistent with best-practice guidelines.MethodA search on Scottish Therapeutics Utility for patients prescribed an average daily dose of opioid equivalent ≥50 mg morphine between 1 July 2019 and 1 October 2019, excluding methadone, cancer pain, or palliative prescriptions. The Faculty of Pain Medicine’s best-practice guidelines were used.ResultsDemographics: 60 patients (37 females), average age 62, 28% registered with repeat opioid prescription, 38% comorbid depression. Length of prescription: average 6 years, 57% >5 years, 22% >10 years. Opioid: 52% tramadol, 23% on two opioids. Indications: back pain (42%), osteoarthritis (12%), fibromyalgia (10%). Initial consultation: 7% agreed outcomes, 35% follow-up documented. Review: 56% 4-week, 70% past year.ConclusionOpioid prescribing guidelines are not followed. The significant issues are: long-term prescriptions for chronic pain, especially back pain; new patients registering with repeat prescriptions; and no outcomes of treatment agreed, a crucial message is the goal is pain management rather than relief. Changes have been introduced at the practice: a patient information sheet, compulsory 1-month review for new patients on opioids, and in-surgery pain referrals.

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