« Go Back

Research Containing: Capillary flow

Capillary Wetting Analysis of the CFE-Vane Gap Geometry

by on 9 June 2015in Physical Sciences No comment

The Vane Gap Capillary Flow Experiments are part of a suite of low-g experiments flown onboard the International Space Station to observe critical wetting phenomena in ‘large length scale’ capillary systems. The Vane Gap geometry consists of a right cylinder with elliptic cross-section and a single central vane that does not contact the container walls. The vane is slightly asymmetric so that two gaps between the vane and container wall are not of the same size. In this study, we identify the critical wetting conditions of this geometry using the Concus-Finn method for both perfectly and partially wetting fluids as a function of container asymmetry. In a cylindrical container in zero-g, single-valued finite height equilibrium capillary surfaces fail to exist if a critical wetting condition is satisfied. This nonexistence results in significant redistribution of the fluids in the container. It will be shown that there could be three critical geometric wetting conditions that include one in each gap region and one for a global shift of bulk fluid which, among the three, is the most significant.

Related URLs:

The capillary flow experiments aboard the International Space Station: Status

by on 9 June 2015in Physical Sciences No comment

This paper provides a current overview of the in-flight operations and experimental results of the capillary flow experiment (CFE) performed aboard the International Space Station (ISS) beginning August 2004 to present, with at least 16 operations to date by five astronauts. CFE consists of six approximately 1–2 kg experiment units designed to probe certain capillary phenomena of fundamental and applied importance, such as capillary flow in complex containers, critical wetting in discontinuous structures, and large length scale contact line dynamics. Highly quantitative video images from the simply performed experiments provide direct confirmation of the usefulness of current analytical design tools as well as provide guidance to the development of new ones. A description of the experiments, crew procedures, performances and status of the data collection and reduction is provided for the project. The specific experimental objectives are briefly introduced by way of the crew procedures and a sample of the verified theoretical predictions of the fluid behavior is provided. The potential impact of the flight experiments on the design of spacecraft fluid systems is discussed in passing.

Related URLs:
http://www.sciencedirect.com/science/article/pii/S0094576509001386

A Novel Device Addressing Design Challenges for Passive Fluid Phase Separations Aboard Spacecraft

by on 9 June 2015in Physical Sciences No comment

Capillary solutions have long existed for the control of liquid inventories in spacecraft fluid systems such as liquid propellants, cryogens and thermal fluids for temperature control. Such large length scale, ‘low-gravity,’ capillary systems exploit container geometry and fluid properties—primarily wetting—to passively locate or transport fluids to desired positions for a variety of purposes. Such methods have only been confidently established if the wetting conditions are known and favorable. In this paper, several of the significant challenges for ‘capillary solutions’ to low-gravity multiphase fluids management aboard spacecraft are briefly reviewed in light of applications common to life support systems that emphasize the impact of the widely varying wetting properties typical of aqueous systems. A restrictive though no less typifying example of passive phase separation in a urine collection system is highlighted that identifies key design considerations potentially met by predominately capillary solutions. Sample results from novel scale model prototype testing aboard a NASA low-g aircraft are presented that support the various design considerations.

Related URLs:
http://dx.doi.org/10.1007/s12217-008-9091-7

Systems and methods for separating a multiphase fluid

by on 9 June 2015in Physical Sciences No comment

Apparatus and methods for separating a fluid are provided. The apparatus can include a separator and a collector having an internal volume defined at least in part by one or more surfaces narrowing toward a bottom portion of the volume. The separator can include an exit port oriented toward the bottom portion of the volume. The internal volume can receive a fluid expelled from the separator into a flow path in the collector and the flow path can include at least two directional transitions within the collector.

Related URLs:
https://www.google.com/patents/US7905946

Preliminary Results from the Capillary Flow Experiment Aboard ISS: The Moving Contact Line Boundary Condition

by on 9 June 2015in Physical Sciences No comment

The Capillary Flow Experiment (CFE) consists of six approximately 2kg test vessels constructed by NASA to probe certain capillary phenomena of fundamental and applied importance. The light weight, low-volume hardware can be shipped to orbit on short notice as cargo space permits and the experiment performed in stand-alone mode by a single crewmember on, for example, the Maintenance Work Area (workbench) of the International Space Station. Video images from the simply performed crew procedures provide highly quantitative data for the confirmation of current analytical design tools as well as directions for further theoretical development. This paper presents a narrative of preliminary results from the first Capillary Flow Experiment (CFE) conducted aboard ISS in August-September 2004. The tests are performed as per of NASA’s Saturday Morning Science Program on ISS and completed in good order by Astronaut Michael Fincke who collected approximately 100 data sets that compare large length scale capillary surface oscillations and damping for two otherwise identical cylindrical tanks differing only in respect to a critical yet uncertain boundary condition at the contact line. Linear, nonlinear, and destabilizing slosh, swirl, axial, and other disturbances are studied. The large data set is being reduced for comparisons to the blind predication of a group of numerical analysis assembled to gauge the accuracy of present methods to predict large length scale capillary dynamics critical to fluids management in spacecraft (i.e. fuels, cryogens, water). The success of the experiment reported herein serves as a testimony to astronaut ingenuity and the perhaps surprisingly flexible fluids laboratory of the ISS for safe and simple fluids experimentation.

Related URLs:

Beverage cup for drinking use in spacecraft or weightless environments

by on 9 June 2015in Physical Sciences No comment

A beverage cup comprised by an open top and at least one channel defined by a corner with an acute angle so placed that the channel runs along the cup side from the cup bottom to the cup rim. In the absence of significant gravitational force as found in microgravity, weightless or weightlessness of spacecraft or the International Space Station, capillary forces between the beverage and the cup wall allow the beverage to creep along the channel and be in near proximity to the open cup rim. Lips placed at or near the channel at the rim can readily sip, drink, and consume the beverage without the need for a straw and without undue spillage for normal drinking motions including toasting. The channel conducts the beverage via capillary forces from the bottom of the cup to the rim until the beverage has been consumed.

Related URLs:

Geometry Pumping on Spacecraft (The CFE-Vane Gap Experiments on ISS)

by on 9 June 2015in Physical Sciences No comment

urrent experiments aboard the International Space Station (ISS) illustrate an extent to which liquid behavior aboard spacecraft can be controlled by wetting and container geometry. The experiments are referred to as the 'Vane-Gap' experiments and are part of a more general set of simple handheld Capillary Flow Experiments1) (CFE) designed and developed at NASA's Glenn Research Center for conduct on ISS. The CFE-Vane Gap experiments highlight the sensitivity of a capillary fluid surface to container shape and how small changes to said shape may result in dramatic global shifts of the liquid within the container. Understanding such behaviors is central to the passive management of liquids aboard spacecraft and in certain cases permits us the ability to move (pump) large quantities (potentially tons) of liquid by a simple choice of container shape. In particular, the Vane-Gap experiments identify the critical geometric wetting conditions of a vane structure that does not quite meet the container wall-a construct arising in various fluid systems aboard spacecraft such as liquid fuel and cryogen storage tanks, thermal fluids management, and water processing equipment. In this paper experimental results are compared with preliminary theoretical and numerical analyses.

Related URLs:

Postflight summary of the Capillary Flow Experiments aboard the International Space Station

by on 9 June 2015in Physical Sciences No comment

This paper provides a summary of the experimental, analytical, and numerical results of the Capillary Flow Experiment (CFE) performed onboard the International Space Station (ISS) from Increment 9 (beginning August, 2004) through Increment 16 (ending December, 2007), with 19 operations by 7 astronauts; M. Fincke, W. McGarthur, J. Williams, S. Williams, M. Lopez-Alegria, C. Anderson, and P. Whitson. CFE consists of 6 approximately 1 to 2kg experiment units designed to probe certain capillary phenomena of fundamental and applied importance, such as capillary flow in complex containers, critical wetting in discontinuous structures, and large length scale contact line dynamics. Highly quantitative video images from the simply performed flight experiments provide immediate confirmation of the usefulness of current analytical design tools as well as provide guidance to the development of new ones. A brief review of the experiments and procedures is provided before reporting the status of the data collection, reduction, and comparisons with both analytic and numerical predictions. The products of the work include design tools for modeling capillary interface dynamics relevant to spacecraft engineering systems. The CFE experimental program was initiated in February 2003 as part of a fast-paced unscheduled payloads/experiments program. All six of the units were performed on standby or at times as part of NASA Saturday Science and all units have been returned to Earth for post flight analysis. The experiments were conducted in stand-alone mode by a single crewmember on the Maintenance Work Area of the ISS.

Related URLs:

Thermophysical characteristics of a wickless heat pipe in microgravity – Constrained vapor bubble experiment

by on 9 June 2015in Physical Sciences No comment

Wickless heat pipes are being studied for use in cooling critical components of spacecraft. The wickless design is thought to produce a simpler and lighter heat transfer system than heat pipes containing wicks or mechanically driven systems. The constrained vapor bubble experiment (CVB) is one such system tested on the International Space Station where the Bond Number (ratio of gravitational force to surface force) is small maximizing the affects of capillarity. The CVB is essentially a square, fused silica spectrophotometer cuvette evacuated and then partially filled with pentane as the working fluid. Along with temperature and pressure measurements, the two-dimensional thickness profile of the menisci formed at the corners of the quartz cuvette was determined using an interferometry based system contained with the station’s Light Microscopy Module (LMM). The CVB can be viewed as a hollow fin and its behavior analyzed using a simple, one-dimensional heat transfer model. That model, coupled with the visual observation of the vapor–liquid distribution inside the fin, provides an enhanced understanding of what the measured temperature and pressure profiles represent and the heat transfer mechanisms controlling the operation of the device. The internal heat transfer processes were found to be very complicated, multi-dimensional, and greatly dependent on internal and external radiative heat transfer. Internal radiative exchange was found to be more significant than originally anticipated as was the effect Marangoni forces on internal convective heat transfer. An analysis of the temperature profiles in conjunction with vapor–liquid interface mapping showed that the system could be separated into a number of discrete operation zones depending on the dominant mode of heat transfer.

Related URLs:
http://www.sciencedirect.com/science/article/pii/S0017931014006334

Dynamic Fluid Interface Experiments Aboard the International Space Station: Model Benchmarking Dataset

by on 9 June 2015in Physical Sciences No comment

This paper introduces a video database reduced from the handheld capillary flow contact line experiments completed aboard the International Space Station during expeditions 9-16, August 2004-November 2007. The simple fluid interface experiments quantify the uncertain impact of the boundary condition at the contact line: the region where liquid, gas, and solid meet. This region controls many significant static and dynamic characteristics of the large length scale capillary phenomena critical to multiphase fluids management systems aboard spacecraft. Difference in fluid behavior of nearly identical static interfaces to nearly identical perturbations are attributed primarily to difference in fluid physics in the vicinity of the contact line. Free and pinned contact lines, large and small contact angles, and linear and nonlinear perturbations are tested for several manually imparted perturbation types (i.e. axial slosh and other modes) to right circular cylinders. The video and sample digitized datasets are made publically available for model benchmarking. As a demonstration of the utility of the database, and in parallel with the experiment effort, blind numerical predication of the dynamic interface response to the experimentally applied input perturbation are offered as an example of current capabilities to predict such phenomena. The agreement and lack of agreement between the experiment and numeric is a guide to improve or verify current analytical methods to predict such phenomena critical to practical spacecraft fluid systems design.

Related URLs:
http://dx.doi.org/10.2514/1.47343