scholarly journals Discussion: “A Bulk-Flow Theory for Turbulence in Lubricant Films” (Hirs, G. G., 1973, ASME J. Lubr. Technol., 95, pp. 137–145)

1973 ◽  
Vol 95 (2) ◽  
pp. 145-146
Author(s):  
V. N. Constantinescu
Keyword(s):  
Flow Theory ◽  
Bulk Flow ◽  
Lubricant Films

A Bulk-Flow Theory for Turbulence in Lubricant Films

1973 ◽  
Vol 95 (2) ◽  
pp. 137-145 ◽  
Author(s):  
G. G. Hirs
Keyword(s):  
Theoretical Basis ◽  
Kinematic Viscosity ◽  
Flow Theory ◽  
Lubricant Film ◽  
Bulk Flow ◽  
Mixing Length ◽  
Lubricant Films

The purpose of this study on the turbulent lubricant film is: 1 To give a brief outline of a new theory called bulk-flow theory; 2 To investigate to what extent results of theories based on law of wall and mixing length concept agree with the newly developed theory; 3 To provide a theoretical basis for the design of bearings lubricated by fluids of low kinematic viscosity.

Nonlinear Analysis of Rotordynamic Fluid Forces in the Annular Plain Seal by Using Extended Bulk-Flow Analysis: Influence of Static Eccentricity and Whirling Amplitude

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Koya Yamada ◽  
Atsushi Ikemoto ◽  
Tsuyoshi Inoue ◽  
Masaharu Uchiumi
Keyword(s):  
Perturbation Analysis ◽  
Flow Analysis ◽  
Flow Theory ◽  
Bulk Flow ◽  
Design Stage ◽  
Fluid Force ◽  
Force Coefficients ◽  
Fluid Forces ◽  
Static Eccentricity ◽  
Harmonic Components

Rotor-dynamic fluid force (RD fluid force) of turbomachinery is one of the causes of the shaft vibration problem. Bulk flow theory is the method for analyzing this RD fluid force, and it has been widely used in the design stage of machine. The conventional bulk flow theory has been carried out under the assumption of concentric circular shaft's orbit with a small amplitude. However, actual rotating machinery's operating condition often does not hold this assumption, for example, existence of static load on the machinery causes static eccentricity. In particular, when such a static eccentricity is significant, the nonlinearity of RD fluid force may increase and become non-negligible. Therefore, conventional bulk flow theory is not applicable for the analysis of the RD fluid force in such a situation. In this paper, the RD fluid force of the annular plain seal in the case of circular whirling orbit with static eccentricity is investigated. The case with both the significant static eccentricity and the moderate whirling amplitude is considered, and the perturbation analysis of the bulk-flow theory is extended to investigate the RD fluid force in such cases. In this analysis, the assumption of the perturbation solution is extended to both static terms and whirling terms up to the third order. Then, the additional terms are caused by the coupling of these terms through nonlinearity, and these three kinds of terms are considered in the extended perturbation analysis of the bulk flow theory. As a result, a set of nonlinear analytical equations of the extended perturbation analysis of the bulk flow theory, for the case with both the significant static eccentricity and the moderate whirling amplitude, is deduced. The RD fluid force for such cases is analyzed, and the occurrence of constant component, backward synchronous component, and super-harmonic components in the RD fluid force is observed in addition to the forward synchronous component. The representation of RD fluid force coefficients (RD coefficients) are modified for the case with significant static eccentricity, and the variation of RD fluid force coefficients for the magnitude of static eccentricity is analyzed. These analytical results of RD fluid force and its RD coefficients are compared with the numerical results using finite difference analysis and experimental results. As a result, the validity of the extended perturbation analysis of the bulk-flow theory for the case with both the significant static eccentricity and the moderate whirling amplitude is confirmed.

A Systematic Study of Turbulent Film Flow

1974 ◽  
Vol 96 (1) ◽  
pp. 118-126 ◽  
Author(s):  
G. G. Hirs
Keyword(s):  
Systematic Study ◽  
Classification System ◽  
Film Flow ◽  
Flow Theory ◽  
Bulk Flow ◽  
Experimental Results ◽  
Flow Theories ◽  
Set Up ◽  
Flow Experiments

Turbulent film flow theories can only be verified on the basis of a large number of experimental results. Since it will be useful to handle these experimental results more or less systematically and to get some idea of the amount of work yet to be done, the first objective of this paper is to set up a classification system for turbulent film flow experiments. The second objective is to verify the bulk flow theory on the basis of the limited number of experimental results available in the literature and to show this theory to be compatible with these results.

Nonlinear Analysis of Rotordynamic Fluid Forces in the Annular Plain Seal by Using Extended Bulk-Flow Analysis: Influence of Static Eccentricity and Whirling Amplitude

2018 ◽  
Author(s):  
K. Yamada ◽  
A. Ikemoto ◽  
M. Uchiumi ◽  
T. Inoue
Keyword(s):  
Perturbation Analysis ◽  
Flow Analysis ◽  
Flow Theory ◽  
Bulk Flow ◽  
Design Stage ◽  
Fluid Force ◽  
Force Coefficients ◽  
Fluid Forces ◽  
Static Eccentricity ◽  
Harmonic Components

Rotor-dynamic fluid force (RD fluid force) of turbo-machinery is one of the causes of the shaft vibration problem. Bulk flow theory is the method for analyzing this RD fluid force, and it has been widely used in the design stage of machine. Conventional bulk flow theory has been carried out under the assumption of concentric circular shaft’s orbit with small amplitude. However, actual rotating machinery’s operating condition often does not hold this assumption, for example, existence of static load on the machinery causes static eccentricity. In particular, when such a static eccentricity is significant, the nonlinearity of RD fluid force may increase and become non-negligible. Therefore, conventional bulk flow theory is not applicable for the analysis of RD fluid force in such situation. In this paper, RD fluid force of the annular plain seal in the case of circular whirling orbit with static eccentricity is investigated. The case with both the significant static eccentricity and the moderate whirling amplitude is considered, and the perturbation analysis of the bulk-flow theory is extended to investigate RD fluid force in such cases. In this analysis, the assumption of the perturbation solution is extended to both static terms and whirling terms up to the third order. Then, the additional terms are caused by the coupling of these terms through nonlinearity, and these three kinds of terms are considered in the extended perturbation analysis of the bulk flow theory. As a result, a set of nonlinear analytical equations of the extended perturbation analysis of the bulk flow theory, for the case with both the significant static eccentricity and the moderate whirling amplitude, is deduced. RD fluid force for such cases are analyzed, and the occurrence of constant component, backward synchronous component and super-harmonic components in RD fluid force is observed in addition to the forward synchronous component. The representation of RD fluid force coefficients (RD coefficients) are modified for the case with significant static eccentricity, and the variation of RD fluid force coefficients for the magnitude of static eccentricity is analyzed. These analytical results of RD fluid force and its RD coefficients are compared with the numerical results using finite difference analysis and experimental results. As a result, the validity of the extended perturbation analysis of the bulk-flow theory for the case with both the significant static eccentricity and the moderate whirling amplitude is confirmed.

scholarly journals Theoretical Solutions for Dynamic Characteristics of Liquid Annular Seals with Herringbone Grooves on the Stator Based on Bulk-Flow Theory

2018 ◽  
Vol 2018 ◽  
pp. 1-13
Author(s):  
Lulu Zhai ◽  
Zhonghuang Chi ◽  
Jia Guo ◽  
Zhenjie Zhang ◽  
Zuchao Zhu
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Flow Theory ◽  
Operating Conditions ◽  
Bulk Flow ◽  
Analysis Method ◽  
The Stability ◽  
Herringbone Grooves ◽  
Better Than ◽  
Annular Seals

Liquid annular seals are primarily used to control the leakage in high-speed turbomachinery, especially in nuclear and petrochemical pumps. In this paper, a theoretical analysis method for dynamic characteristics of liquid seals with herringbone grooves on the stator is proposed based on bulk-flow theory. Steady-state velocities and leakage rates within the upstream and downstream spiral parts and the middle plain part taking account of the pumping effects are figured out first with the inertia term of the fluid within the whole seal. Then, the dynamic characteristics of the whole seal are solved based on Childs’ finite-length solutions and verified by comparing with experimental hydraulic forces. Moreover, characteristic coefficients and instability parameters of the herringbone-grooved teeth-on-stator (TOS) seals and teeth-on-rotor (TOR) seals of the same size under different pressure differences are predicted and compared in detail. The influences of the lengths of constituent parts on the dynamic characteristics and instability parameters of the model seals are theoretically investigated. The results show that the stability of the TOS seal is much better than that of the TOR seal under most operating conditions. And the lengths of the middle plain part significantly affect the dynamic characteristics and the stability parameter.

Nonlinear Analysis of Rotordynamic Fluid Forces in the Annular Plain Seal by Using Extended Perturbation Analysis of the Bulk-Flow Theory (Influence of Whirling Amplitude in the Case With Concentric Circular Whirl)

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Atsushi Ikemoto ◽  
Tsuyoshi Inoue ◽  
Kazukiyo Sakamoto ◽  
Masaharu Uchiumi
Keyword(s):  
Perturbation Analysis ◽  
Large Amplitude ◽  
Flow Analysis ◽  
Flow Theory ◽  
Bulk Flow ◽  
Rotating Shaft ◽  
Fluid Force ◽  
Fluid Forces ◽  
Shaft System ◽  
Large Amplitude Vibration

The bulk-flow theory for the rotordynamic (RD) fluid force has been investigated for many years. These conventional bulk-flow analyses were performed under the assumption and restriction that the whirl amplitude was very small compared to the seal clearance while actual turbomachinery often causes the large amplitude vibration, and these conventional analyses may not estimate its RD fluid force accurately. In this paper, the perturbation analysis of the bulk-flow theory is extended to investigate the RD fluid force in the case of concentric circular whirl with relatively large amplitude. A set of perturbation solutions through third-order perturbations are derived explicitly. It relaxes the restriction of conventional bulk flow analysis, and it enables to investigate the RD fluid force for the whirl amplitude up to about a half of the clearance. Using derived equations, the nonlinear analytical solutions of the flow rates and pressure are deduced, and the characteristics of the RD fluid force are investigated in both radial and tangential directions. The influence of the whirl amplitude on the RD fluid force is explained and validated by comparing with computational fluid dynamics (CFD) analysis. These results are useful for the analysis and prediction of frequency response of the vibration of the rotating shaft system considering the RD fluid forces.

Fisiopatología de la hidrocefália idiopática de presión normal (parte 3): sistemaa glinfático

2016 ◽  
Vol 21 (2) ◽  
pp. 28-37
Author(s):  
Oscar Solís-Salgado ◽  
José Luis López-Payares ◽  
Mauricio Ayala-González
Keyword(s):  
Amyloid Beta ◽  
Interstitial Fluid ◽  
Amyloid Β ◽  
Bulk Flow ◽  
Polyethylene Glycols ◽  
Brain Interstitial Fluid ◽  
El Sistema ◽  
Arterial Pulsation ◽  
The Brain

Las vías de drenaje solutos del sistema nervioso central (SNC) participan en el recambio de liquido intersticial con el líquido cefalorraquídeo (LIT-LCR), generando un estado de homeostasis. Las alteraciones dentro de este sistema homeostático afectará la eliminación de solutos del espacio intersticial (EIT) como el péptido βa y proteína tau, los cuales son sustancias neurotóxicas para el SNC. Se han utilizado técnicas experimentales para poder analizar el intercambio LIT-LCR, las cuales revelan que este intercambio tiene una estructura bien organizada. La eliminación de solutos del SNC no tiene una estructura anatómica propiamente, se han descubierto vías de eliminación de solutos a través de marcadores florecentes en el espacio subaracnoideo, cisternas de la base y sistema ventricular que nos permiten observar una serie de vías ampliamente distribuidas en el cerebro. El LCR muestra que tiene una función linfática debido a su recambio con el LIT a lo largo de rutas paravasculares. Estos espacios que rodean la superficie arterial así como los espacios de Virchow-Robin y el pie astrocitico junto con la AQP-4, facilitan la entrada de LCR para-arterial y el aclaramiento de LIT para-venoso dentro del cerebro. El flujo y dirección que toma el LCR por estas estructuras, es conducido por la pulsación arterial. Esta función será la que finalmente llevara a la eliminación de estas sustancias neurotóxicas. En base a la dependencia de este flujo para la eliminación de sustancias se propone que el sistema sea llamado “ la Vía Glinfática”. La bibliografía así como las limitaciones que se encuentran en esta revisión están dadas por la metodología de búsqueda que ha sido realizada principalmente en PubMed utilizando los siguientes términos Mesh: Cerebral Arterial Pulsation, the brain via paravascular, drainage of amyloid-beta, bulk flow of brain interstitial fluid, radiolabeled polyethylene glycols and albumin, amyloid-β, the perivascular astroglial sheath, Brain Glymphatic Transport.

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