Fluid Patterns Introduction
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Fluid Patterns Introduction We breathe air in and out without two Doing Science sheets are meant special projects for individual stu• thinking about its presence. Because to show that air movement outdoors dents. In either case, it is important it is invisible, we draw conclusions and indoors is not chaotic but some• that you try out the activities before about some of its properties by the what ordered. The third and fourth introducing them to the students. The movement it creates. Outdoors, leaves show how very beautiful patterns can experience of working with the mate• rustle on trees and debris and paper be created with water in a more con• rials will also help you to understand blow about in the wind. Indoors, trolled environment. The beautiful the other comments in the Notes to smoke from a cigarette, or fine vortices formed with the food color the Teacher. Always be aware that particles of dust in bright sunlight or detergent in water in the last two however effective your presentation, indicate that, even in a still room, the activities show spiraling motion more some students will need help in air is moving. Because such happen• clearly than the bubbles and smoke understanding and interpreting the ings are so common, we often over• of the first two activities. Also, the procedures and directions in the look the beautiful forms and patterns Doing Science series goes from the Doing Science sheets. that these movements create. Smoke large scale to the small scale with the The remaining commentary in this rises and folds in on itself, forming a explicit^uggestion that approximate booklet is meant to provide back• continually changing flux of spirals models of large scale phenomena ground which will help you under• and curves, sensuous and visibly can be done on a small scale. Overall, stand the phenomena being Doing Science sets up situations entrancing. investigated and place the studies in in which enticing phenomena will Water also can take on many beauti• the context of how the scientist encourage close observation and intu• ful shapes, from the rolling waves at works. What follows attempts to itive understanding of fluid motion. the beach to the fascinating whirlpool answer such questions as what moti• that forms as a bathtub empties. Milk The sheets for Doing Science are vates scientists to study a particular dropped into a still cup of coffee aimed at the student. This approach phenomenon and the methods they forms mushroom shapes that quickly will allow you to do the activities use to investigate it. dissolve. In all of these continually either as a whole class pursuit, or as changing situations, there are repeti• tions of some basic forms. Patterns emerge after long observation. HEAT TRANSFER The aim of this packet is to help you SPACECRAFT SAND-WATER FUNCTIONAL REENTRY PROBLEMS and your students discover the beauty INTERACTION ANALYSIS SAND RIPPLES. DUNES and fascination of air and water move• EROSION PROBLEMS BRIDGE DESIGN ment. It is a phenomenon that has MEANDERING OF RIVERS DESIGN OF WINGS fascinated people since early time. TIDAL WAVES. DEEP WATER WAVES, SHIP WAVES MAXIMUM LIFT Stori^, mythologies and elements of HARBOUR DESIGN MINIMUM DRAG JET NOISE SHIP DESIGN: HULLS ACOUSTICS religious practice, such as the Taoist PURE SONIC BANGS PROPELLERS . MATHEMATICS i CONCORDE SUBMARINES symbol, were modeled on the proper• FISH PROPULSION ties of the vortex or spiral. SUBSONIC M < 1 CIVIL & TRANSONIC M-1 Many natural systems involving air NAUTICAL AERODYNAMICS SUPERSONIC M > 1 ENGINEERING HYPERSONIC M > > 1 or water create patterns that are some type of vortex. It has intrigued biolo• CHEMICAL gists for some time that even living BIOLOGICAL GEOPHYSICS f ATMOSPHERE. WEATHER organisms take on the form of frozen 8t NUCLEAR LARGE SCALE CIRCULATION ENGINEERING TRADE WINDS JET STREAM movement. The gnarls in the trunk of ELASTIC FLUIDS LOCAL WEATHER. HURRICANES SUSPENSIONS: GENERATION OF WAVES BY WIND some trees and the mushroom itself PARTICLES IN LIQUIDS 'ASTROPHYSICS OCEAN MOTION GAS BUBBLES IN LIQUIDS THERMAL CIRCULATION look like solid models of liquid move• PHYSIOLOGICAL FLUID MECHANICS GULF STREAM ment. At the same time, much of our BLOOD CIRCULATION THE EARTH'S INTERIOR MANTLE CONVECTION modern technology depends on an TECTONICS CONTINENTAL DRIFT understanding of fluid movement. PLANETARY ATMOSPHERES EARTH'S MAGNETIC FIELD DYNAMO THEORY Airplanes and boats provide the most 'SOLAR WIND. INTERPLANETARY GAS\ THE SUN STARS PULSARS obvious examples. But the design of SUN SPOTS QUASARS automobiles, the circulation of air in a THERMAL CONVECTION large building, and the working of heart valves are other examples (Fig. 1). The Doing Science section of the packet suggests a series of activities Fig. 1 Fluid dynamics touches upon many different areas of modern technology as well as a diverse which can start you and your students range of natural phenomena. Grouped under the different disciplines are specific problems which illustrate the diversity. Adapted from a (.hart by H.K. Moffatt. from Fluid Dynamics, ed. exploring fluid motion. They show Balian and Peube, 7977, Courtesy Gordon and Breach. London. how air and water movement can be made visible and help to provide a focus for these explorations. The first Science, Art and Fluid Patterns If you look closely at the steam scudding across the sky, and the experimental techniques and theories coming off a freshly brewed cup of changing colors and shapes of an oil are continually being developed to coffee, you will see that a variety of slick on a gently moving pool of expand and clarify the various mani• spirals, curling vortices and curving water. And scientists are not immune festations of fluid motion (Fig. 1). lines continually appear and disap• to that delight, even though scientists pear. When you slowly add cream to use a great deal of machinery and in• the coffee, you produce yet more strumentation. They do have interests mushroom-shaped patterns which in the beauty of everyday phenomena, swirl atop the surface. A blown-out esthetics, and elegance. The funda• match gives off smoke similar in pat• mental motivation for creative scien• tern to that of the steam. In the Doing tists is the recognition of patterns Science activities, you will observe in nature. smoke from a burning string or in• Scientists begin to diverge from art• cense, and move food color through a ists when it comes to explaining the solution of starch and water. The patterns. Scientists need to undertake moving patterns produced in all of systematic observations and experi• these situations are beautiful to watch. ments to understand the common In fact, you can drop food color in characteristics in a set of similar phe• water for hours on end because of the nomena. Further refinement results hypnotic quality of the motion. in abstract formal relationships J6# Similar kinds of patterns can be expressed in mathematical terms. found on a much larger scale. Large Fluid motion itself incorporates a whirlpools can form in fast-moving wide range of related phenomena. rivers or streams. Tornadoes are Fluids move in other fluids and spawned from giant thunderheads, around solid objects. Smoke drifts up displaying a beautiful form, but into the sky from a tall chimney, and destroying everything in its path. currents in the ocean mix waters of Today we too often regard science different temperatures and densities and art as two separate undertakings. on a grand scale, the salmon swims This is true as far as the overall process upstream in a fast moving river to and the final product are concerned. spawn, and the whale navigates great But science and art often share a com• distances in the ocean. "f-~ "P* >' •) -fTf* • s*™. ^..n. „fMw mon origin in fascination with the The fundamental rules of fluid dy• natural world. Both scientists and art• namics can be applied to these diverse ists seek patterns in nature, and have environments and movements. But been interested in air and water move• much is still not understood. New ment through the ages. The paintings of J.M.W. Turner and Vincent Van Gogh reflect this fascination. Sometimes these two different approaches to the study of nature reside in one person. Leonardo da Vinci is among history's most creative scientific inventors and at the same time one of the greatest artists. The drawings in his notebooks were based on close observation and continual experimentation; they were as much works of art as records of his experi• mentation. One phenomenon that fascinated da Vinci throughout his life was the movement of air and water. His notebooks contain sketches of flowing water that show in detail the vortex patterns in rivers and streams. He was the first to closely observe tur• bulent motion and to study vortices created by obstacles in flowing water. Fig. 2 These two examples are among many drawings of water in motion found in da Vinci s There is a great sensual delight in notebooks. The portrait may be of da Vinci himself. watching smoke from a fire, clouds Copyright reserved Reproduced by gracious permission of Her Majesty Queen Elizabeth 11. Royal Library. Windsor Castle. In each of the activities in Doing Making Fluid Motion Visible Science, students use a simple mate• rial to make visible air and water movements: bubbles and smoke for wind and air currents; food color and detergent for water. Each environ• ment requires a suitable material for observation. You would find that even small soap bubbles are inade• quate for detecting drafts of air indoors, but that smoke is an effective indicator. Scientists take a similar approach when they want to study how air or water moves around objects. They also use smoke or dye; but the photos in Figures 3, 4 & 5 show they have devised other techniques.