ESTIMATION OF WATER ENTRY FORCES, SPRAY PARAMETERS AND SECONDARY IMPACT OF FIXED WIDTH WEDGES AT EXTREME ANGLES USING FINITE ELEMENT BASED FINITE VOLUME AND VOLUME OF FLUID METHODS

In this paper, water entry of wedges with deadrise angles ranging from 10 to 80 degrees at two different velocities is simulated. Impact forces, spray parameters, cavity formation above the chine, and secondary impact forces due to the cavity formation are investigated with particular focus on the extreme angles. To this end, a two dimensional two-phase Finite-Element based Finite-Volume (FEM-FVM) code is developed and validated against experimental data with good compliance. Free surface modeling in this software is accomplished by applying Volume of Fluid (VOF) method. In addition to the extraction of impact forces, secondary impact forces, spray characteristics, and cavity formation, it is demonstrated that there is a combined critical length and entry velocity where the spray formation stops and the spray vanishes. It is also shown that the cavity and secondary impact do not occur under these circumstances. Moreover, it is concluded that for these particular cases, there is a maximum secondary impact force that occurs for the deadrises angles less than 20o

CFD-DEM Hybrid Modelling of Multiphase Gravity-Driven Granular Flows

«RÉSUMÉ:Les matériaux granulaires se trouvent dans de nombreux processus industriels, les sciences naturelles et notre vie quotidienne. La prédiction du comportement complexe des écoulements granulaires est cruciale pour une conception plus efficace, valide et fiable dans de nombreux problèmes d'ingénierie. En outre, les écoulements granulaires entraînés par l’effet de gravité sous forme de coulées de débris, glissements de terrain, et les avalanches pourraient entraîner des conséquences dévastatrices en raison de leur longue distance parcourue, de leur vitesse d'écoulement élevée et de leur mouvement massif. Compte tenu de ces derniers, la prédiction du comportement et du mécanisme des écoulements granulaires devient nécessaire et d'une importance cruciale.» et «----------ABSTRACT: Granular materials are ubiquitous in many industrial processes, the natural sciences, and our everyday life. Prediction of the complex behavior of the granular flow is crucial for a more efficient, effective, and reliable design in many engineering problems. Furthermore, gravity-driven granular flows in forms of debris flows, landslides, and avalanches could lead to devastating consequences due to their long runout distance, their high flow velocity and their massive movement. Considering these devastating consequences, prediction of the behavior and mechanism of granular flows become necessary and of crucial importance.

Asymmetric Water Entry of Twin Wedges with Different Deadrises, Heel Angles, and Wedge Separations using Finite Element Based Finite Volume Method and VOF

Asymmetric water entry of twin wedges is investigated for deadrise angles of 30 and 50 degrees, and heel angles of 5, 10, 15, and 20 degrees as well as wedge separation ratios of 1 and 2. Finite Element based Finite Volume method (FEM-FVM) is used in conjunction with Volume of Fluid (VOF) scheme for the targeted analyses. Free surface evolution and impact forces versus time are determined and comparisons of the maximum force of the wedges against each other are presented for all the considered cases. It is demonstrated that the impact force on the second wedge is always greater than the first one by a minimum of 6% and maximum of 146% which is a very significant increase in the impact force and may cause high accelerations and damage to the structure. It is also observed that the mentioned effects increase with decreasing deadrise angle and increasing heel angle

Magnetic sponges for localized and controlled drug delivery with drug combination therapy

Systemic drug administration (i.e., intravenous injection), leading to drug circulation throughout the body can be associated with adverse side effects. Alternatively, localized drug delivery systems have been developed to focus drug concentrations at target sites. This method of delivery has been widely accepted in orthopedic infection management where the poor blood supply hampers antibiotics from reaching the infected site. Antibiotic-loaded bone cement beads have been approved for clinical delivery systems for the localized treatment of bone infections (osteomyelitis). The beads, however, have some shortcomings such as incompatibility with some antibiotics, and poor drug elution, which relies on unregulated passive diffusion. This dissertation proposes an on-demand drug delivery device that can control the release pattern using a controlled magnetic field application. The drug delivery device has the same configuration as conventional bone cement beads. It provides a sustained antibiotic discharge through a PMMA shell with multiple holes, while incorporating a magnetic porous PDMS at its core to manage the release profile via external magnetic fields. The magnetic sponge’s magneto-mechanical properties are investigated under non-uniform magnetic fields. Unlike proposed models that explore the effect of uniform magnetic fields, this study presents an analytical model that demonstrates the magnetic sponge response to the magnetic field gradient. The findings of this study and the development of the drug delivery device can provide adjustable released content controlled by the strength of the applied magnetic field. The in vitro experiments confirm the antibacterial efficacy of discharged gentamicin and silver against both gram-positive and gram-negative bacteria with extended bactericidal activity up to six days after drug combination. The ex vivo assessment demonstrated a successful drug discharge upon implantation with a controllable release profile using a magnet. Furthermore, to address the increasingly prevalent problem of antibiotic-resistant bacteria, a synergy study was conducted on gentamicin and silver nitrate. The results showed a significant improvement in the antibacterial efficiency once the two agents are combined, inhibiting the growth of MRSA and E. coli by more than 3log10CFU/mL. Exploiting the drug combination therapy in conjunction with a controllable localized drug delivery device may provide a more efficient therapy for treating osteomyelitis.Applied Science, Faculty ofBiomedical Engineering, School ofGraduat

Design, fabrication, and characterization of a magnetic porous pdms as an on-demand drug delivery device

We introduce a novel, on-demand drug delivery device based on a biocompatible magnetic sponge. The sponge is made of a porous polydimethylsiloxane (PDMS) mixed with carbonyl iron (CI) particles. The sponge is deformed under a magnetic field and consequently leads to releasing its contents. As a proof of concept study, three different CI/PDMS wt% ratios of 50%, 100%, and 150% were selected where, the 100% showed the most deformation under various magnetic fields. Although this sponge can solely be used as a potential drug delivery agent, a separate reservoir has been fabricated to protect the sponge and control the release rate. The final device has a diameter of 6 mm with a thickness of 2 mm. Controlled release of methylene blue (MB) and docetaxel (DTX) have been investigated to demonstrate the consistency and flexibility in adjusting the release rate from the device to suit different treatment requirements. Ex vivo tissue implantation has also been accomplished. This device is able to be implanted and deliver therapeutic agents at prescribed dosages.Applied Science, Faculty ofMechanical Engineering, Department ofGraduat

ESTIMATION OF WATER ENTRY FORCES, SPRAY PARAMETERS AND SECONDARY IMPACT OF FIXED WIDTH WEDGES AT EXTREME ANGLES USING FINITE ELEMENT BASED FINITE VOLUME AND VOLUME OF FLUID METHODS

In this paper, water entry of wedges with deadrise angles ranging from 10 to 80 degrees at two different velocities is simulated. Impact forces, spray parameters, cavity formation above the chine, and secondary impact forces due to the cavity formation are investigated with particular focus on the extreme angles. To this end, a two dimensional two-phase Finite-Element based Finite-Volume (FEM-FVM) code is developed and validated against experimental data with good compliance. Free surface modeling in this software is accomplished by applying Volume of Fluid (VOF) method. In addition to the extraction of impact forces, secondary impact forces, spray characteristics, and cavity formation, it is demonstrated that there is a combined critical length and entry velocity where the spray formation stops and the spray vanishes. It is also shown that the cavity and secondary impact do not occur under these circumstances. Moreover, it is concluded that for these particular cases, there is a maximum secondary impact force that occurs for the deadrises angles less than 20o

CFD-DEM Modeling of Dense Sub-Aerial and Submerged Granular Collapses

Sub-aerial (dry) and submerged dense granular collapses are studied by means of a three-phase unresolved computational fluid dynamics-discrete element method (CFD-DEM) numerical model. Physical experiments are also performed to provide data for validation and further analysis. Validations show good compatibility between the numerical and experimental results. Collapse mechanism as well as post-collapse morphological parameters, such as granular surface profile and runout distance, are analyzed. The spatiotemporal variation of solid volume fraction is also investigated. The effect granular column aspect ratio is studied and found to be a key factor in granular morphology for both submerged and dry conditions. The volume fraction analysis evolution shows an expansion and re-compaction trend, correlated with the granular movement

The Manufacture and Characterization of Silver Diammine Fluoride and Silver Salt Crosslinked Nanocrystalline Cellulose Films as Novel Antibacterial Materials

There is an unmet need for biocompatible, anti-infective, and mechanically strong hydrogels. This study investigated the use of poly vinyl alcohol (PVA), polysaccharides, and nanocrystalline cellulose (CNC) to deliver silver in a controlled manner for possible use against oral or wound bacteria. Silver was included in solvent cast films as silver diammine fluoride (SDF) or as nitrate, sulphate, or acetate salts. Hydrogel formation was assessed by swelling determinations and silver release was measured using inductively coupled plasma methods. Antibacterial studies were performed using Gram-positive and negative bacteria turbidity assays. PVA formed homogenous, strong films with SDF and swelled gently (99% hydrolyzed) or vigorously with dissolution (88% hydrolyzed) and released silver slowly or quickly, respectively. CNC-SDF films swelled over a week and formed robust hydrogels whereas CNC alone (no silver) disintegrated after two days. SDF loaded CNC films released silver slowly over 9 days whereas films crosslinked with silver salts were less robust and swelled and released silver more quickly. All silver loaded films showed good antibacterial activity. CNC may be crosslinked with silver in the form of SDF (or any soluble silver salt) to form a robust hydrogel suitable for dental use such as for exposed periodontal debridement areas.Applied Science, Faculty ofDentistry, Faculty ofPharmaceutical Sciences, Faculty ofNon UBCBiomedical Engineering, School ofOral Health Sciences (OHS), Department ofReviewedFacult