44
P. Liu
Who can block the splitting and breaking up?
Don’t forget the way back in troubled times.
A sudden splitting of the great eddy.
Order and disorder always go hand in hand.
Note: Who can block the splitting and breaking up? It means that when
Re reaches a certain value, the laminar flow will turn into turbulence, which
is determined by internal instability and cannot be blocked. Don’t forget the
way back in troubled times—it means that average motion after turbulence
is distinguishable (controllable). A sudden splitting of the large eddy means
that large eddies suddenly break up into small eddies. Order and disorder
always go hand in hand—indicates the coherent structure of large eddies in
a turbulent flow field.
1.7 Turbulence Phenomenon and Its
Characteristics
As far as turbulence is concerned, Da Vinci, the Renaissance Italian allround scientist, was the first to observe in detail. He observed the eddies
and turbulences qualitatively on the beach and recorded the flow structure of
the eddies and turbulences in his notes. In a famous turbulence painting,
he wrote that the clouds were torn apart by the strong wind, the sand
particles rose from the beach, and the trees stooped down. The splitting
and fragmentation of turbulence, entrainment of turbulent eddies, and wall
shear are clearly depicted. Since Reynolds’ transition experiment in 1880,
Reynolds put forward the concept of time mean in 1883, which considered
that the instantaneous motion of turbulence consisted of time mean motion
and pulsating motion, but Reynolds called turbulence tortuous motion at
that time. In 1895, Reynolds put forward the Reynolds equations describing
the time-averaged motion of N-S equation by assuming that the instantaneous motion of turbulence satisfies Navier–Stokes equations. From then on,
turbulence research began to embark on the road of closed turbulence equation (In fact, whether the instantaneous physical quantity of motion satisfies
the N-S equations has been debated at the beginning. The main concern is
whether Newton’s law of internal friction, which characterizes the constitutive
relationship between stress and deformation rate in fluid motion, is applicable to instantaneous turbulence. In addition, N-S equations require that
physical quantities be continuous differentiable functions, but in fact, the
P. Liu
Who can block the splitting and breaking up?
Don’t forget the way back in troubled times.
A sudden splitting of the great eddy.
Order and disorder always go hand in hand.
Note: Who can block the splitting and breaking up? It means that when
Re reaches a certain value, the laminar flow will turn into turbulence, which
is determined by internal instability and cannot be blocked. Don’t forget the
way back in troubled times—it means that average motion after turbulence
is distinguishable (controllable). A sudden splitting of the large eddy means
that large eddies suddenly break up into small eddies. Order and disorder
always go hand in hand—indicates the coherent structure of large eddies in
a turbulent flow field.
1.7 Turbulence Phenomenon and Its
Characteristics
As far as turbulence is concerned, Da Vinci, the Renaissance Italian allround scientist, was the first to observe in detail. He observed the eddies
and turbulences qualitatively on the beach and recorded the flow structure of
the eddies and turbulences in his notes. In a famous turbulence painting,
he wrote that the clouds were torn apart by the strong wind, the sand
particles rose from the beach, and the trees stooped down. The splitting
and fragmentation of turbulence, entrainment of turbulent eddies, and wall
shear are clearly depicted. Since Reynolds’ transition experiment in 1880,
Reynolds put forward the concept of time mean in 1883, which considered
that the instantaneous motion of turbulence consisted of time mean motion
and pulsating motion, but Reynolds called turbulence tortuous motion at
that time. In 1895, Reynolds put forward the Reynolds equations describing
the time-averaged motion of N-S equation by assuming that the instantaneous motion of turbulence satisfies Navier–Stokes equations. From then on,
turbulence research began to embark on the road of closed turbulence equation (In fact, whether the instantaneous physical quantity of motion satisfies
the N-S equations has been debated at the beginning. The main concern is
whether Newton’s law of internal friction, which characterizes the constitutive
relationship between stress and deformation rate in fluid motion, is applicable to instantaneous turbulence. In addition, N-S equations require that
physical quantities be continuous differentiable functions, but in fact, the