Simulation des écoulements diphasiques dans les stations de pompage

The purpose of the present study is to develop numerical tools for two-phase flow ploblems in pumping stations. Reliable simulation methods of two-phase flow are inevitable in nuclear engineering field because computer programs are important design tools for nuclear reactors which are exposed to severe ambient conditions of high temperature, high pressure and gamma ray irradiation. Mock-up tests of nuclear thermal-hydraulics are very difficult. Hitachi Ltd. has created advanced computer programs for multi-dimensional two-phase flow to analize reactor systems and components. The numerical methods enable accurate and stable interface calculation in spite of large density ratio between the phases, because non-staggered finite volume method, which is suitable for treatment of discontinuity, and minimum numerical diffusion are adopted. The multi-dimensional computer programs employ two types of two-phase flow model. The first one is the extended two-fluid model, which has capability of both interface tracking and ordinary two-fluid model calculations. This model is appropriate for the present purpose because it can treat free surface of channels and entrained bubbly mixture due to breaking waves. The second one is the improved VOF (Volume of Fluid) method in which PLIC (Piecewise Linear Interface Calculation) technique was employed. The interface state calculation is simplified by approximating cubic calculation cells to spherical ones. These computer program were applied to hydraulic studies in Hitachi Industries Co., Ltd., a vender of fluid machinery and pumping systems. It is necessary to evacuate air downstream from siphon outlets as bubble entrainment by water flow in order to operate the plant effectively after pumping station start-up. Experiments were carried out by using a reduced scale test-section. The test section was made of transparent acryl and the cross-section was rectangular. Free surface of water layer on the inclined wall and entrained bubbly mixture into the water pool due to water layer collision with free surface were observed by a video camera. The extended two-fluid model results of transient water level and pressures in the simulated siphon outlets were in good agreement with the experimental data. The predicted pressure histories at the crest and the pump site were in good agreement with the experimental data. The sedimentation in a inlet channel of a pump station was carried out. Three dimensional free surface flow was calculated by the improved VOF method and behavior of suspended sediment in the flow field is calculated. The surface wave velocity in the shallow channel was in good agreement with the theoretical one. Sediment particles had size distribution and drag force and gravity and buoyancy was taken into consideration. Critical tractive force of the sediment on floor was estimated from Schields’ correlation. The predictions of sedimentation area and suspended fraction agreed well with experimental data. These results showed that the present computer programs were able to treat key two-phase flow phenomena in pumping stations

原発性限局性尿道アミロイドーシスの1例

Amyloidosis of the urethra is a rare disease. The clinical appearance resembles carcinoma of the urethra, so that biopsy is required to make the appropriate diagnosis. Once primary localized amyloidosis of the urethra has been diagnosed, selection of the appropriate treatment for each case becomes important. We report a case of primary localized amyloidosis in the male anterior urethra. This case was treated successfully with urethral dilatation

男性化手術を施行した女子先天性副腎皮質過形成(21-hydroxylase欠損)の1例

21・hydroxylase欠損による先天性副腎皮質過形成をもつ25歳女子(戸籍上は男子)症例に対して2度にわたる男性化手術をおこなった.1度目は卵巣子宮附属器切除術と索切除術であり, 2度目は11ヵ月後の尿道形成術と両側偽睾丸挿入術である.術後の排尿機能と勃起の状態は良好であった.A 25-year-old female with simple virilizing type of congenital adrenocortical hyperplasia due to 21-hydroxylase deficiency was treated surgically with masculinizing operations which consisted of two-stage procedures. The first procedure was chordectomy associated with excision of both gonads and female internal genitalia. Eleven months later, the second procedure consisting of urethroplasty and implantation of testicular prosthesis was performed. The postoperative course was successful in terms of urination and penile erection