Numerical Investigation on the Effect of Blade Loading on Unsteady Sheet Cavitation Patterns

Cavitation commonly manifests itself as vapour structures attached to the suction surfaces of impeller, runner or propeller blades. The numerical study carried out here seeks to correlate the changes in the behaviour of sheet cavitation to variations in blade geometry. The analysis is run for a two-dimensional stationary cascade. The streamwise loading distribution is the metric used to characterise the geometry. It determines the rate and amount of work generated across the channel and is directly connected to blade surface pressure. In this study, the test sample consists of a set of varying blade profiles characterised by specific loading configurations: foreloaded, aft-loaded or bespoke distributions. Time-resolved simulations of the cavitating flow are generated to study cavity behaviour. Computations are run through Fluent using the SST URANS formulation. The Zwart-Gerber-Belamri homogeneous cavitation model is used to treat cavitation. A range of behaviours are observed for the cavitation patterns. Variations are found in inception conditions, shape and sheet stability. For the latter, two dynamic regimes are identified with a transition point that varies according to the loading profile. A pair of tradeoff relations are also observed: hydrodynamic efficiency versus suction performance and suction performance versus cavity stability. The results demonstrate the capacity of the loading distribution to affect cavitation dynamics.

Surgical Technique and Clinically Relevant Resection Cavity Dynamics Following Implantation of Cesium-131 Brachytherapy in Patients With Brain Metastases

BACKGROUND Cesium-131 (Cs-131) brachytherapy is used to reduce local recurrence of resected brain metastases. To ensure dose homogeneity and reduce risk of radiation necrosis, interseed distance and cavity volume must remain stable during delivery. OBJECTIVE To investigate the efficacy of the “seeds-on-a-string” technique with intracavitary fibrin glue in achieving cavity volume stability. METHODS We placed intraoperative Cs-131 brachytherapy in 30 cavities postresection of brain metastases. Seeds-on-a-string were placed like barrel staves within the cavity with fibrin glue. Serial magnetic resonance imaging occurred postoperatively. Preoperative tumor volumes were compared with postoperative cavity volumes to evaluate volume stability. Thirty patients who underwent postresective stereotactic radiosurgery (SRS) were used as a control group for volumetric comparison. RESULTS Cs-131 and SRS patients exhibited consistent cavity shrinkage over the median 110-day follow-up (P < .001), with total median shrinkage of 56.5% (Cs-131) and 84.8% (SRS). During the first month when ≈88% of Cs-131 dosage is delivered, however, there was nonsignificant volume decrease in the Cs-131 group (median 22.0%; P = .06), whereas SRS patients showed significantly more shrinkage (46.7%; P = .042). No events of radiation necrosis occurred in either group. CONCLUSION Cs-131 patients exhibited significantly less cavity shrinkage than SRS patients during the first critical month with 88% Cs-131 dose delivery. This significant difference in shrinkage suggests that the intracavitary seeds-on-a-string technique facilitates increased cavity stability, promoting more homogenous dose delivery.

The Research Progress of Key Technology on Building Energy Underground Storage in Salt Rock

With unique advantages, salt cavern gas storage was got more and more attention in the field of oil industry in the world. It is a complicated system engineering to build an underground dissolved cavity to store gas with a certain shape in salt layer. Combined with the characteristics on the gas storage construction in salt layer, and based on the cavity destination and implementation process of cavity construction, cavity construction technology of salt cavern gas storage was conducted a comprehensive exposition. Through analyzing the formation process of gas storage cavity, well-types of cavity construction, water recycle modes, steps of dissolving cavity, adjustment modes of two wells distance, shape control method, roof protection technology, sealing detection, cavity stability and many other techniques were put forward on the respect of cavity construction process, cavity control and detection method. And the column combination modes of cavity construction, the methods of determining water injection flow and the measures of protecting cavity stability were recommended. It is meaningful for the design and construction of the cavity construction of salt cavern gas storage.